Question 477702
Jim's work in an hour
4 hours…………………….. 1 desk
Divide by 4 both sides
4/4 hour…………………………… 1/4 desk
1 hour…………………….. 1/4 desk
So Jim can build one fourth of the desk in 1 hour

Matt's work in an hour
6 hours............ 1 desk
Divide by 6 both sides
6/6 hour............ 1/6 desk
1 hour.............. 1/6 desk
So Matt can build one sixth of the desk in 1 hour

In an hour Jim will complete 1/4 of desk and Matt will complete 1/6 desk

1 hour = (Jim's work + Matt's work)
1 hour = 1/4+1/6 desk
1 hour	= (3+2)/12
1 hour	= 5/12 desk
Multiply both sides by 12/5
12/5 * 1 hour = 5/12  * 12/5 desk
12/5 hours = 1 desk
2 2/5 hours
or 
2.40 hours.