Number of females = f Total number of people in audience = n
0.4n = f f + (f+ 100) = n 2f + 100 = n
Find n: f = 0.4n --> Replace f with 0.4n in the equation 2f +100 = n
2(0.4n) + 100 = n --> Multiply out the brackets 0.8n + 100 = n --> Subtract 0.8n from both sides 100 = 0.2n --> To get n, multiply both sides by 5 n = 500