If 2x + 5y = 21 and x + y = 3, then what is the value of x?

a x=-5
b x=2
c x=5
d x=-2

D

Step-by-step explanation:

Given the 2 equations

2x + 5y = 21 → (1)

x + y = 3 → (2)

Rearrange (2) expressing y in terms of x, by subtracting x from both sides

y = 3 - x ← Substitute into (1)

2x + 5(3 - x) = 21 ← distribute and simplify left side

2x + 15 - 5x = 21

- 3x + 15 = 21 ( subtract 15 from both sides )

- 3x = 6 ( divide both sides by - 3 x = - 2 → D

8(-10x+3.5y-7)

8×-10x + 8×3.5y + 8×-7

-80x + 28y - 56

therefore

-80x+28y-56 is the correct answer