When f(x) is substituted with a number, you just plug the number into wherever you see x:
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f(12) = 3/2x + 14
f(12) = 3/2(12) + 14
f(12) = 18 + 14
f(12) = 32
f(-4) = 3/2x + 14
f(-4) = 3/2(-4) + 14
f(-4) = -6 + 14
f(-4) = 8
f(0) = 3/2(0) + 14
f(0) = 0 + 14
f(0) = 14
