Opposite
additive inverse
"the product of" ⇒ ___ * ___
86 ⇒ 86 . . . . . fills first blank
and
the depth of the river ⇒ d . . . . . fills second blank.
Your expression is
86 * d
Because the angles are supplementary, they add to 180 degrees.
I solved this by dividing

which gives me 30 degrees.
multiply 30 by 5 gives you 150.
and 30 + 150 = 180