Final answer:
To evaluate the expression 9x-2x with 7 substituted for x, combine like terms to get 7x which simplifies to 7(7) when substituting 7 for x. The expression evaluates to 49 which is reasonable.
Step-by-step explanation:
To evaluate the expression 9x-2x when x is substituted with 7, we first simplify the algebraic expression by combining like terms. This is done by subtracting the coefficient in front of the second x from the coefficient in front of the first x.
9x - 2x = (9-2)x = 7x
Now that we have the simplified expression 7x, we substitute 7 in place of x and multiply:
7(7) = 49
So, the expression evaluates to 49 when x is substituted with 7.
Lastly, we check the answer to see if it is reasonable.
Multiplying 7 by 7 does indeed give us 49, which is a reasonable result for this calculation.