Let's use Cross-multiplication:
2mi ------------------------>15min
x mi------------------------->45min
So:
2/x = 15/45
Solving for x:
Multiply both sides by x:
x*(2/x) = x* 15/45
2 = 15x/45
Multiply both sides by 45:
45*2 = 45*(15x/45)
90 = 15x
Divide both sides by 15:
90/15 = 15x/15
6 = x
x = 6mi
