72:24=15:_____
72 : 24 = 15 : ____ set up as :
72 / 24 = 15 / x
Notice that the first ratio can be reduced to 3/1.......so we have
3/1 = 15 / x cross-multiply
3 *x = 15 * 1
3x = 15 divide by 3 on both sides
x = 5 and that's the missing value
