Answer:
≥
Step-by-step explanation:
(v+4)t=66
t=66/(v+4)
...
(v-4)t=42, using t found above in this equation gives you:
66(v-4)/(v+4)=42 perform indicated multiplication on the left side
(66v-264)/(v+4)=42 multiply both sides by (v+4)
66v-264=42v+168 add 264 to both sides
66v=42v+432 subtract 42v from both sides
24v=432 divide both sides by 24
v=18
So his normal bicycling speed with no wind is 18 mph.