Step-by-step explanation:
y = -3x² + mx + 10
dy/dx = -6x + m.
When dy/dx = 0, -6x + m = 0. => x = m/6.
We have y = -3(m/6)² + m(m/6) + 10 = 37.
=> -m²/12 + m²/6 = 27
=> -m² + 2m² = 324
=> m² = 324
=> m = 18 or m = -18.
Answer:

Step-by-step explanation:
Let
denotes number of pencils, markers, erasers respectively.
For Andrea:

For Justin:

For Virginia:

On subtracting equations (i) and (ii), we get

Put
in equation (i)

Put
in equation (iii)

Multiply equation (iv) by 5 and equation (v) by 6 and then subtract both the equations.

Put
in equation 

Put
in equation (i)

Your answer will be 7.50. What I did was take 1.25 and times it by 6.
let's set up an equation:
x-4=9
solve normally:
x=13