Area is not measured in feet, but square feet. Assuming you mean an area of 90 feet by 63 feet, this is equal to 90 x 63 = 5670 square feet.
90
63 sq feet
21 x 3 yards/foot = 63 feet
If that's 12 x 90 feet, it's 1080 square feet. If that's 12 x 90 inches, it's 7.5 square feet.
60 square feet
90 x 90 = 8100 square feet
Multiply 90 x .63= 56.7 is 63% of 90
90 x 7 = 630 sq ft
3 x 30 = 90 square feet (90 ft2).
90
63 sq feet
1,449 square feet.
2,079
There are 63*3 = 189 feet in 63 yards, since there are 3 feet in a yard.
90 x 130 = 11,700 square feet.
150 x 90 = 13,500 square feet
There are: 90*49.5 = 4455 square feet