When evaluating a piecewise function, the fist step is to determine the applicable domain. Then the function defined for that domain is the one that is used for the evaluation.
<h3>A.</h3>
x = 0 is in the domain x < 5, so the applicable function is f(x) = x+4.
f(0) = 0 +4 = 4
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<h3>B.</h3>
x = 6 is in the domain 5 ≤ x < 7, so the applicable function is f(x) = 8.
The length is 21 feet. The break down of it. You set up a proportion 5 1/4 over 3 1/2 = 31 1/2 over x. Cross multiply 31.5 times 3.5= 110.25 divided by 5.25 which gives you 21.