Answer:
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:
Answer: x = 4
