For f(1), substitute 1 in for x in the right-hand side of the equation:
f(1) = 2(1) + 7,
so f(1) = 3 + 7
so f(1) = 10.
For f(-2), substitute -2 in for x in the right-hand side of the equation:
f(-2) = 2(-2) + 7,
so f(-2) = -4 + 7,
so f(-2) = 3.