Answer
1$\frac{1}{4}$ heads
Work Step by Step
Total number of heads of lettuce = 5$\frac{1}{2}$
Heads of lettuce used for sandwiches = 1$\frac{1}{2}$
Heads of lettuce used for salads = 2$\frac{3}{4}$
Remaining heads of lettuce = 5$\frac{1}{2}$ - 1$\frac{1}{2}$ - 2$\frac{3}{4}$
=$\frac{11}{2}$ - $\frac{3}{2}$ -$\frac{11}{4}$
=$\frac{8}{2}$ - $\frac{11}{4}$
= $\frac{8}{2}\times$ $\frac{2}{2}$ - $\frac{11}{4}$
=$\frac{16}{4}$ - $\frac{11}{4}$
=$\frac{5}{4}$
=1$\frac{1}{4}$ heads
