For this case we must simplify the following expression:

We solve the operation of the second parenthesis, taking into account that different signs are subtracted and the sign of the major is placed:

We multiply:

We eliminate the parentheses:

We add similar terms, taking into account that equal signs are added and the same sign is placed:

Answer:
The simplified expression is: 
90 x 7 = 630 square feet total
0.5 fluid ounce per sq ft
630 x 0.5 = 315 fluid ounces are needed
B) y = -2x
when x = a
y = -2a
when x= 2a
y = -2(2a) = -4a
A point has D) zero dimensions
Each angle is 90 degrees because 90 times 3 is 270.