a1 =-88 S11=22
a11-? d-?

[tex]s = \frac{a1 + a11}{2} \times n = \frac{ - 88 + a11}{2} \times 11 \\ 22 = \frac{ - 88 \times a11}{2} \times 11 \\ 2 = \frac{ - 88 + a11}{2} \\ 4 = - 88 + a11 \\ a11 = 92 \\ \\ a11 = a1 + d(11 - 1) \\ 92 = - 88 + 10d \\ d = \frac{92 + 88}{10} = 18[/tex]