Workers

It is 5. Al can mow a lawn in two hours. Together, Al and Bob can mow a lawn in 6/5 hours, because (2*3)/(2+3)=6/5. In 6 hours, they can mow 6/(6/5), or 5 lawns.

its simple there are 6 hours al can 3 in 6 hours and bob 1 lawn in 3 hours means 2 lawns in 6 hours there four 3+2=5

Al mows 3 lawns in 6 hours, or 1 lawn in 2 hours. So, in 1 hour, he can mow half a lawn.

Bob mows 1 lawn in 3 hours. So, in 1 hour, he can mow one-third of a lawn.

Together, they mow $\frac{1}{2} + \frac{1}{3} = \frac{5}{6}$ of a lawn in 1 hour.

So, in 6 hours, they can mow $\frac{5}{6} \times 6 = \boxed5$ lawns.

Al's work rate is $\frac{3}{6}$ , which means 3 lawns per 6 hours. It simplifies to $\frac{1}{2}$ . Now let's look at Bob. Bob has a work rate of 1 lawn per 3 hours. Adding these two work rates together gives the time they work together on one lawn, which is $\frac{5}{6}$ , meaning 5 lawns per 6 hours. Read the question again. It says how many lawns they can mow in 6 hours? Well, we already have the answer, bringing us to $\boxed{5 \text{ lawns}}$