Estimate. Then find the sum or difference

Estimate
26.42
-9.8

Mary used 1/7 of a spool of ribbon to complete 4 projects. she used the same amount of ribbon on each project. how much ribbon did she use on each project?

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

Solve with work both bert and ernie received an increase in their weekly salaries. bert's salary increased from $520 to $520. ernie's salary went from $580 to $645. find the percent of increase for each salary. what was the larger of the two percents ?