We were told that Aubrey paints 4 square feet of her house each minute.
Recall that 1 minute = 60 seconds.
The statement can be written as
Aubrey paints 4 square feet of her house each 60 seconds
If x represents the number of square feets that she paints in 20 seconds, it means that
4 = 60
x = 20
By cross multiplying, it becomes
60 * x = 4 * 20
60x = 80
x = 80/60
x = 1.333
Rounding to the nearest tenth, it becomes 1.3 square feet
She paints 1.3 square feet in 20 seconds