John's family visited his grandmother over the weekend. The drive to her house took 2 hours at their usual speed. The trip took 15 minutes longer because traffic was bad and they had to drive 5 mph slower. How many miles away is Johns grandmother's house?

Let the normal speed = x mph

The way to his grandmothers they drove 2x miles

Return trip was 2.25(x-5)

Set those equal and solve for x:

2x = 2.25(x-5)

Simplify:

2x = 2.25x -11.25

Subtract 2.25x from both sides:

-0.25x = -11.25

Divide both sides by-0.25:

X = 45

The usual speed is 45 mph.

So now 2 hours at 45 mph = 90 miles to his grandmothers house

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step-by-step explanation: