so, the original cost was $100
Step-by-step explanation
the easiest way to solve this is by using a rule of three
then
Step 1
Let
orginal price=100% = unknow value= x
aved= 20%=$200,
Step 2
make the proportions and solve for x
![\begin{gathered} \text{if } \\ x\rightarrow100 \\ \text{then} \\ 200\rightarrow20 \\ \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/7tc04boa9yej5rtkyskkfq41puwgsc15vq.png)
the ratios are equals, so the proportion is
![(x)/(100)=(200)/(20)](https://img.qammunity.org/2023/formulas/mathematics/college/bdnu1orywjbsonr9fv0ph4bsychw7s57dh.png)
finally, isolate x
![\begin{gathered} (x)/(100)=(200)/(20) \\ cross\text{ multiply} \\ 20\cdot x\text{=10}0\cdot200 \\ 20x=20000 \\ \text{divide both sides by 20} \\ (20x)/(20)=(20000)/(200) \\ x=20 \\ x=100 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/xljkdd197jzpz6n3mogwzuvlga39vad68k.png)
so, the original cost was $100
I hope this helps you