Answer:
15
Step-by-step explanation:
let's begin by find our variables!
in this case June= x, July = y, and August = z
now that we found our variables let make an equation
x + y + z = 40
we know that x (June)= 12 y (July)= 13 so let's plug that, in place of the variables
12 + 13 + z = 40
Combine like terms
25 + z = 40
Subtract 25 out of 25 and out of 40
25 - 25 + z = 40 - 25
z= 15
now let's plug in all our variable values x = 12; y = 13; z = 15
12 + 13 + 15 = 40 ✓
