Question #1:
Put the markup as a decimal.
80% = 0.8
Multiply.
0.8 * 300 = 240
Add.
300 + 240 = $540
The price of the sofa after markup is $540
Question #2:
Divide.
8 / 90 = 0.0888888
Multiply.
0.0888888 * 100% = 8.88888%
Round.
8.89%
8.89% is the percent of 90 is 8.
Question #3:
Turn percentage into a decimal.
80% = 0.8
Multiply
300 * 80 = 240
80% of 300 is 240
Question #4:
Put the markup as a decimal.
8.01% = 0.0801
Multiply.
2,500 * 0.0801 = $200.25 (markup)
Add.
2,500 + 200.25 = $2,700.25
The price after markup is $2,700.25