Chapter 1, Equations and Inequalities - 1.6 Solve Inequalities - 1.6 Exercises - Problem Solving - Page 47: 58c

See below.

Since $1$ mile equals $1.61$ kilometers we can get the appropriate inequalities, by multiplying the speeds by $1.61$. Hence here the legal speeds (if $x$ is the speed in kph) are: $1.61\cdot45\leq x\leq1.61\cdot70\\72.45\leq x\leq112.7$. Hence here the illegal speeds (if $x$ is the speed in kph) are: $0\cdot1.61\leq x\lt1.61\cdot45 \cup x\gt1.61\cdot70\\0\leq x\lt72.45 \cup x\gt112.7$.