Answer:
231 sq. ft.
Step-by-step explanation:
Total of anything is 100%
45% are painted, so not painted:
100 - 45 = 55%
The number of sq. ft. that still needs to be painted is basically 55% of 420 (total sq. ft.).
55% in decimal is 55/100 = 0.55
Now we multiply this with total:
0.55 * 420 = 231 sq. ft. (remaining)