Answer:
10 donuts and 10 brownies
Step-by-step explanation:
In this case we must solve the system of equations that do not say in the statement:
at least 20 must be, therefore:
x + y = 20 => x = 20 - y
1.5 * x + 2.5 * y = 40
replacing:
1.5 * (20 - y) + 2.5 * y = 40
30 - 1.5 * y + 2.5 * y = 40
y = 40 - 30
y = 10
now for x:
x = 20 - 10
x = 10
therefore, to be a minimum of 20, they must be 10 donuts and 10 brownies