Question 1160642
let b = the number of boys
let g = the number of girls.
you get:
b + g = 42
2/5 * b + 1/2 * g = 19
multiply both sides of the second equation by 2 and leave the first equation as is to get:
b + g = 42
4/5 * b + g = 38
subtract the second equation from the first to get:
b - 4/5 * b = 4
multiply both sides of this equation by 5 to get:
5b - 4b = 20
combine like terms to get:
b = 20
since b + g = 42, then g must be equal to 22.
you have:
b = 20
g = 22
b + g = 42
2/5 * b + 1/2 * g = 2/5 * 20 + 1/2 * 22 = 8 + 11 = 19
solution is the number of boys in the canteen is 20 and the number of girls in the canteen is 22.