Answer
a. $f(x)=15+0.05x$
b. $g(x)=5+0.07x$
c. $500$ text messages.
Work Step by Step
a. Based on the given information, for plan-A, we have $f(x)=15+0.05x$
b. Based on the given information, for plan-B, we have $g(x)=5+0.07x$
c. Let $f=g$, we have $15+0.05x=5+0.07x$ which gives $0.02x=10$ and $x=500$ text messages.
