Question

3x/9=12/17

Answer 1

multiply by 9*17 to get

3x*9*17/9 = 12*9*17/17

also known as cross-multiplying, because then the previous denominators cancel out, giving

3x*17 = 12*9
51x = 108
x = 108/51 = 36/17

or, you can factor out the 3 first, since

3(x/9) = 3(4/17)
x/9 = 4/17
x = 36/17