F(7) means f(x) when x = 7. The x is replaced with 7.
So we'll replace every x with 7 to go from x = 7 to 3-x = 3-7 = -4
Put another way
f(x) = 3-x
f(7) = 3-7
f(7) = -4
Answer: -4
Ur not dumb!!! i graphed the line for u here. i suggest watching some khan academy videos for extra practice!
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