Question

What equation can equal 66 but also equal 25

Answer 1

Equations have two sides which equal each other.  The equation itself doesn't really equal anything.

Perhaps the question is what equation has solutions (also known as roots) equal to 66 and 25?

There are infinitely many, including

(x-66)(x-25)=0

That's an equation, so we can just call it done.  But let's expand because we can:

(x-66)(x-25)=x² - 91x + 1650

Answer: x² - 91x + 1650 = 0