Answer:
∠a=44,∠b=47, ∠c=89
Explanation:
we can note that
∠a+∠b+∠c=180
hence,
3x+5+5x-18+7x-2=180
therefore,
3x+5x+7x+5-18-2=180
15x-15=180
15x=180+15
15x=195
x=

then, x=13.
with this values we can find all the angles:
∠a=3x+5 ⇒∠a=3(13)+5⇒∠a=39+5⇒∠a=44
∠b=5x-18⇒∠b=5(13)-18⇒∠b=65-18⇒∠b=47
∠c=7x-2⇒∠c=7(13)-2⇒91-2⇒∠c=89
We can corroborate these result by adding them.
∠a+∠b+∠c=
44+47+89=180
Thats right !!