Answer
a) $f(2)=15$
b) $f(-1)=10$
Work Step by Step
a) When $x=2,$ the corresponding $y-$value in the given diagram is $
15
.$ Hence,
\begin{array}{l}\require{cancel}
f(2)=15
.\end{array}
b) When $x=-1,$ the corresponding $y-$value in the given diagram is $
10
.$ Hence,
\begin{array}{l}\require{cancel}
f(-1)=10
.\end{array}