1) [(c - 7)(c + 7)*5c] / [10cd*2(c + 7)] = (c - 7) /(4c)
2) [(b - d)*3bd] / [d*(b - d)*(b + d)] = (3b) / (b + d)
3) [(x - 5)² * (x - 4)*(x + 4)] / [3*(c + 4) * 2 * (x - 50] = [(x - 5)(x - 4)] / 6
4) [(1 - a)*(a + 2b)²] / [4*(a + 2b)*3*(1 - a) = (a + 2b) / 12
5) [2*(b - 5a)] / [(5a - b)*(5a + b)] = (-2) / (5a + b)