Use benchmarks to estimate each sum or difference. 4/5 + 8/9

a. about 1 1/2
b. about 1 3/4
c. about 1 8/9
d. about 2

Use benchmarks to estimate each sum or difference. 17/18 + 3/7

a. about 1/4
b. about 1/2
c. about 0
d. about 1