Can You Solve This Logic Puzzle?

This is from a sample paper for the Online Mathematics Challenge 2020.

Source

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[kuga]

3 + 5 = 16 ( false)
4 + 7 = 30 ( false)
1 + 1 = 2 ( true )

[Tom_Cruise]

am i the only one who got 0?
(3+1)*(5-1)=16
(4+1)*(7-1)=30
(1+1)*(1-1)=0

[JoelWetzel]

I thought it would be 4 based on a pattern I saw: 3x5+1; 4x7+2; 1x1+3. I know so little.

[spring]

I'm sorry but this is not a logic test. by labeling it as a logical test, you mislead people into solving the problem outside the conventional mathematical paradigm and into finding some different correlation between the numbers which are not related to direct, obvious computation.
this problem should have been labeled as: _solve the following mathematical equation_ .

[pokemaniacqolem]

3+5 = 16 I interpret as "3 x 5 +1"
4+7 = 30 I interpret as "4 x 7 +2"
Therefore 1+1 is "1x1+3=4" :)

[jaytep]

Thumbnail is a bit misleading but overall good video.

[qwertyTRiG]

Neat that there was no need to solve a, b, and c themselves.

[pepehimovic]

3a + 5b + c = 16
4a + 7b + c = 30

We want to know what a + b + c equals

9a + 15b + 3c = 48
8a + 14b + 2c = 60

a + b + c = -12

[atharvkapila]

(3+1)*(5-1)=16
(4+1)*(7-1)=30
(1+1)*(1-1)=0 That's how i thought of it and it ain't wrong.

[rcabr]

I've also found a simple solution:
(3+1) x (5-1) = 16
(4+1) x (7-1) = 30
So...
(1+1)x(1-1) = 0

Of course we can create any logic to associate the number... but I liked this one

[sunchess]

3×5=15+1=16
4×7=28+2=30
1×1=1+3=4 that's my answer

[hammerhead]

My solution
(3*5)+1=16
(4*7)+2=30
(1*1)+3 =4

[chandrashekarchandu]

My ans is 4 and this how I got it :
3 * 5 + 1=16
4 * 7 + 2 = 30
1 * 1 + 3 = 4

[Gideon_Judges]

The question in the thumbnail was way more open-ended. For example floor(mean(x, y)^2) satisfies the first two equations, and so 1+1=1 would be the third.

[davisatdavis]

The way I solved it was I looked at it as a simple function. Before 3+5, you'd have 2+3, then 1+1. And subtract 14 as it goes down. And that still gives me -12.

[martin-rsgf]

3 + 5 = 16 --> 3x5 [15] + 1 [first digit of 15] = 16
4 + 7 = 30 --> 4x7 [28] + 2 [first digit of 28] = 30
1 + 1 = 2

[sandhyarao]

3+5=16, logic (3*5)+(5-3)-1,
4+7=30, logic(4*7)+(7-4)-1,
So logic is (a*b)+(b-a)-1,
So (1*1)+(1-1)-1=0
This can also be used

[jussinevavuori]

I came up with "0" from seeing the thumbnail with an operation of (x * y) + (|x - y| - 1)

[erikkonstas]

I just figured out that a+2b=14 and then figured that 3a+5b+c-2a-4b=a+b+c,

[milanfanas]

I've seen a lot of tests in which "c" is not constant throughout the expressions but it lineary increases according to the position of the expression.
So in this case you would have
a1 * b1 + 1
a2 * b2 + 2
a3 * b3 + 3
and so on.
When such tests have a multiplicity of solutions they are either malformed or they just need more example cases to constrain the possible answer.