Simplify the expression x^2+3x-28/x^2-7x+12

X^2 + 3x - 28 factors to (X+7)(X-4)
X^2  - 7X + 12 factors to (X-4)(X-3)
Now we see that the equation is [(X+7)(X-4)]/[(X-4)(X-3)]
By dividing the top and bottom by (X-4), we see that the equation equals (X+7)/(X-3).