Question 484184
Your doubt is correct.
As always, make x = what is asked for, the total distance.
Speed = Distance / time.
So Time = Distance / speed.
The trip out will take (time T) = (dist x/2) / (speed 40)
The trip back will take (time T) = (dist x/2) / (speed 45)
Total time: {{{(x/2)/40)}}} + {{{(x/2)/45}}} = 4
Solve for x:
mult by 2 * 5: {{{x/8 + x/9 = 40}}}
mult by 72: {{{9x + 8x = 2880}}}
Div by 17: x = 169.4 miles.
Note that your attempt is an excellent "reasonable" test.
It is off by only 10 football fields.