What’s the answer please

Question

The speed of a stream is 5 mph. A boat travels 100 miles upstream in the same time it takes to travel 150 miles downstream. What is the speed of the boat in sti water?

Answer 1

100 = t(b-5)

150 =t(b+5)

150 = tb+5t

100 = tb-5t

60= 10t

t = 6 hours

100=6(b-5)

b-5 =100/6

b = 100/6 +5 = 16 2/3 +5 = 21 2/3 mph = boat speed in still water