You mean the formula is wrong? Yes, I copied your =(C2/D2-E2)/(12.5/F2/G2*7.8) directly. Is there a #DIV/0! If that's the reason, I'll tell you, because your D2, F2, and G2 are all divisible numbers, and if there are spaces or zeros in those 3 numbers, the formula is wrong. His message is "division by zero error", so you just need to keep these 3 cells not empty or not 0.

Again, your formula =(C2/D2-E2)/(12.5/F2/G2*7.8) is correct. it doesn't matter if 12.5 and 7.8 are one parameter.