Answer is 2 hours to paint the whole room
Step by step
We can solve this with cross multiply
4/7 hours to paint 2/7 of a room
X hours to paint 1 room (7/7)
4/7 over 2/7 = x hours / 1 room
Cross multiply
2/7x = 4/7 divided by (1)
2/7x = 4/7
Divide both sides by 2/7 to solve
When you divide a fraction you flip the divisor and multiply
2/7 * 7/2 x = 4/7 * 7/2
x = 2