Can You Find The Number Whose Square Is 3 Less Than 4 Times The Number.?

We'll let that number be a variable 'x'

Now write the equation in terms of x just as you described;

x² = -3 + 4x

Now solve.  Since it's second order, we'll probably get two answers.

x² -4x + 3 = 0

(x - 3)(x - 1) = 0

x = 3, x = 1

Now check the answers

x² = -3 + 4x

(3)² = -3 + 4(3)
  9   =  -3 + 12
so that one checks

(1)² = -3 + 4(1)
  1   = -3 + 4
and that checks too.

So the answers are 3 and 1.