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A. x = 4

Step-by-step explanation:

Solve for x:

x + 4 (x + 5) = 40

4 (x + 5) = 4 x + 20:

4 x + 20 + x = 40

Grouping like terms, 4 x + x + 20 = (x + 4 x) + 20:

(x + 4 x) + 20 = 40

x + 4 x = 5 x:

5 x + 20 = 40

Subtract 20 from both sides:

5 x + (20 - 20) = 40 - 20

20 - 20 = 0:

5 x = 40 - 20

40 - 20 = 20:

5 x = 20

Divide both sides of 5 x = 20 by 5:

(5 x)/5 = 20/5

5/5 = 1:

x = 20/5

The gcd of 20 and 5 is 5, so 20/5 = (5×4)/(5×1) = 5/5×4 = 4:

x = 4

no not all of them.

step-by-step explanation:

some of them have a square base.

step-by-step explanation: