Value of two variable when only one equation is given. Question- $5^{72}+5^{73}+5^{74}+5^{75} = x \times 5^y$ Also given- both x and y are natural numbers. > Options are 72, 84. 80 and 74 I had figured out- $$5^{72}(5^0+5^1+5^2+5^3) = x \times 5^y$$ $$\Rightarrow156 = \frac {x\times5^y}{5^{72}}$$ I don't know what to do next. Am I on the right track?

it means $$156\cdot 5^{ 72 }=x\times 5^{ y }\\\ x=156,y=72$$