Answer: L = 14
Concept:
Here, we need to understand the idea of evaluation.
When encountering questions that gave you an expression with variables, then stated: "If x = a, y = b, z = c" (a, b, c are all constants), this means you should substitute the value given for each variable back to the expression.
Solve:
Given information
W = 7
P = 42
Given expression
P = 2L + 2W
Substitute values into the expression
42 = 2L + 2 (7)
Simplify by multiplication
42 = 2L + 14
Subtract 14 on both sides
42 - 14 = 2L + 14 - 14
28 = 2L
Divide 2 on both sides
28 / 2 = 2L / 2
Hope this helps!! :)
Please let me know if you have any questions