How to apply Chargaff's rule in order to solve genetics problems?

Chargaff's rules states that DNA from any cell of all organisms should have a 1:1 ratio (base Pair Rule) of pyrimidine and purine bases and, more specifically, that the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine. This pattern is found in both strands of the DNA. They were discovered by Austrian chemist Erwin Chargaff. (1952). "On the deoxyribonucleic acid content of sea urchin gametes"

First parity rule
The first rule holds that a double-stranded DNA molecule globally has percentage base pair equality: %A = %T and %G = %C. The rigorous validation of the rule constitutes the basis of Watson-Crick pairs in the DNA double helix model.

Second parity rule
The second rule holds that both %A ~ %T and %G ~ %C are valid for each of the two DNA strands.[2] This describes only a global feature of the base composition in a single DNA strand.

[dwaipayandattaroy]

I thought U and T combines to form 60% any how C and G would be 40%/2 is 20%, if Uracil in there then it's pair is T, but if Thaimin in there then it's pair is A, emphasis on the template, if template gas U coding will be T, if template is T or A it will be nice versa, T never codes to U, but U codes to T, similarly A never codes to U, basically I figured out that both, U and A codes for T. If rna then A for A, U for T, C for C and G for G on dna strand, but if dna to dna then ATGC will code as TACG