1 answer
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Walking speed --- x km/h
bus speed = x+90 km/h
solve:
4/x + 5/(x+90) = 5/6
multiply each term by 6x(x+90) and simplify the resulting quadratic
before using the quadratic formula. You will get 2 answers, reject the negative one.
btw, that is some fast bus, its speed makes no sense for a school bus