Solve for y in the following proportion
2:y = 4:5
Proportions work the same as equal fractions:
2/y = 4/5 Cross-multiply -->
2*5 = 4*y
Alternatively, you can compare the fractions:
Since the 1st numerator is 1/2 the 2nd numerator, the 1st denom (y) is half of the 2nd denom (5)
