#### Answer

$a_{16}$ + $b_{18}$ = -59 + 88 = 29

#### Work Step by Step

From graph
First term $a_{1}$ = 1
Second term $a_{2}$ = -3
Third term $a_{3}$ = -7
Sequence = 1, -3, -7, . . . . .
Common difference (d) = -7 + 3 = -3 - 1 = -4
By formula $a_{n}$ = $a_{1}$ + (n-1) d
$a_{16}$ = 1 + ( 16 - 1)(-4) = 1 + (15$\times$-4) = 1 - 60 = -59
First term $b_{1}$ = 3
Second term $b_{2}$ = 8
Third term $b_{3}$ = 13
Sequence = 3, 8, 13, . . . . .
Common difference (d) = 13 - 8 = 8 - 3 = 5
By formula $b_{n}$ = $b_{1}$ + (n-1) d
$b_{18}$ = 3 + ( 18 - 1)5 = 3 + (17$\times$5) = 3 + 85 = 88
$a_{16}$ + $b_{18}$ = -59 + 88 = 29