The question above tells us that 30% of A is 45% of B, and that the sum of A and B is 50.
We can translate both of these into equations:
0.30(A) = 0.45(B)
A + B = 50￼
We can solve for B in terms of A:
￼A = 0.45(B)/0.30 = 1.5(B)
Since A = 1.5B, we can plug 1.5B in for A in the second equation:
￼A + B = 1.5(B) + B = 50
2.5(B) = 50
B = 50/2.5
So, B = 20 and the correct answer is (A).