A:B = 2:3
A=126
B=?
126/2=63
63x3=189
A=126
B=189
A:B = 126:189
4/15
Multiple the numerator by numerator, and denominator by denominator, then simplify
B because you multiply every number by 4.
Ex. 30 x 4 = 120
120 x 4 = 480
480 x 4 = 1,920
1,920 x 4 = 7,680
Hopefully that helps you :)