Question 413362
1/3 was painted by 7 men in 45 days so you take 

7*45 = 315 for 1/3 of the bridge so you need 2/3 or twice as much for the unpainted part of the bridge so you have 315 * 2 giving you 630

You only have 42 days left so you take 630 and divide by 42 and get 15

they would need to hire 15 more painters to finish in time.