Question 973233
In one hour, Bill mows (1/2) of the lawn, and with Tom can mow (1/1.5)  of the lawn.

Together, they can mow, in one hour (1/2) + (1/x)=(1/1.5)

Multiply everything by 6x to clear fractions.

3x+6=4x
x=6 hours.  It takes Tom 6 hours to mow the lawn.  In one hour the two mow (1/2)+(1/6)=2/3.  In the next half hour, they mow (1/4)+ (1/12)=(1/3), that finishes it up.