Calculate the inverse of the matrix and find the values for a, b,c, and d

Which sums are equal to 1hold 6/8? choose all answers that are correcta.1/8+6/8b.12/8+2/8c.8/8+1/8+1/8+1/8+1/8+1/8+1/8d.8/8+6/8

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.

Afarmer has a large field that is x feet in length. he wants to fence in a rectangular section in the middle of the field , leaving a length of 100 feet of open field behind each end of the fenced rectangle.he also wants the width of the fenced-in space to be 100 feet less than its length. find the expressions to represent the length and width of the fenced section of the field