Halp me plass me halp

Can someone me with my hwplz(only the circled ones)

List x1, x2, x3, x4 where xi is the left endpoint of the four equal intervals used to estimate the area under the curve of f(x) between x = 4 and x = 6. a 4, 4.5, 5, 5.5 b 4.5, 5, 5.5, 6 c 4.25, 4.75, 5.25, 5.75 d 4, 4.2, 5.4, 6

Sweet t saved 20 percent of the total cost of the green-eyed fleas new album let there be fleas on earth. if the regular price is $30 how much did sweet save