SAT Question 7fac16fb: Linear Functions answer and explanation with Desmos solution

The value of $f(20)$ can be found by evaluating the function $f(x)=\frac{7}{10}x+55$ for $x=20$. Substituting $20$ for $x$ in this function yields $f(20)=\frac{7}{10}(20)+55$, or $f(20)=69$. Therefore, the value of $f(20)$ is $69$.