Answer:
The price of the microwave before the sale was $150
Explanation:
The formula to calculate percentage change between two time periods is p=N−OO⋅100 where p is the percentage change, N is the new price and O is the old price.
In this problem we have been given the percentage change (p=−30%) and the new price (N=105). Substituting these into the formula and solving for O while keeping the equation balanced gives:
−30=105−OO⋅100
−30100=105−OO⋅100100
−0.3=105−OO
−0.3=105O−OO
−0.3=105O−1
1−0.3=105O−1+1
0.7=105O
0.7O=105OO
0.7O=105
0.7O0.7=1050.7
O=15
