We have M is a point on side AB of a triangle ABC such that AM=BM=CM. If angles A and B are respectively x and 70∘
Now By isosceles triangle - ∠ACM=x and ∠BCM=70 ∠ACB=∠ACM+∠MCB ∠ACM=∠CAM=x[ As AM=AC] ∠MCB=∠CBM=70∘[ As BM=MC] ∠ACB=x+70∘ Now use the triangle property - ∠CAM+∠CBM+∠ACB=180 ⇒x+70+x+70=180 ⇒2x+140=180 ⇒2x=180−140 ⇒2x=40 ⇒x=20 Now 3x+25∘=3×20+25 =60+25=85∘