12. a) x/3 = 24/18
If we simplify 24/18 by dividing both the numerator and denominator by 6 we get 4/3
Thus x/3 = 4/3 and since we can directly compare both fractions we can see that x = 4
b) 2/(20 - x) = 3/x
We can cross-multiply to get:
3(20 - x) = 2x
60 - 3x = 2x
60 = 5x
x = 12
