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

the ratios are equals, so the proportion is

finally, isolate x

so, the original cost was $100
I hope this helps you