We are given 5 boys for every four girls. We could set up an equation and solve for x.
5x+4x=198 9x=198 x=22 now plug in x = 22 back for 5x to find the total number of boys 5(22) =110 boys we could also let x = 22 for 4x to find the total number of girls (even though we're not asked to do this) 4(22) = 88 girls
