Math

I'm doing some word problems on finding the areas of rectangles, its just like all complicated. I don't understand how to do them. For example:

A square field had 3 m added to its length and 2m added to its width. The area is 90 m2(squared). Find the length of a side of the original field.

So first you get (x+3)(x+2)=90, right?
then you get x2+5x+6=90
then x2+5x=84

How do you go on? How do you figure out x? I don't get it! I have other problems like those, could you tell me how to figure out a problem with x2 and something x = a number in general? Please help!

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  1. Take your step:
    x^2 + 5x + 6 = 90
    Now:
    x^2 + 5x - 84 = 0

    Factor by inspection or use the quadratic formula to solve for x.
    A hint is what two factors of 84 differ by 5?

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