On Thursday, rrr centimeters of rain fell on Deborah's garden. On Saturday, 15\%15%15, percent more rain fell on the garden.
The expression r+0.15rr+0.15rr, plus, 0, point, 15, r describes the number of centimeters of rain Deborah's garden got on Saturday. We can also use the expression 1.15r1.15r1, point, 15, r to represent the same quantity.