Question

how to simplify (3(x-7)/((x+2)(2x-1))*(4x^(2)+6x-4)/(4x-28))

Answer 1

Distribute out the denominator for the first giving
3(x-7) / 2x^2 + 3x - 2
Do the same for the numerator for the second to get
2x^2 + 3x - 2 / (4x - 28)
Cancel out the two leaving you with
3(x-7) / (4x-28)
Pull out the 4 from the denominator and cancel out
3(x-7) / 4(x-7) = 3/4