Adam has sticks of the following lengths: (3x+4) (2x+10) (x+12)cm
he puts all 3 sticks together to make a triangle. the triangle is isosceles. calculate the 3 possible values of x.

Option I
(3x+4)cm =(2x+10)cm
3x-2x=6
x=6
Option II
(3x+4)= (x+12)
3x-x=12-4
2x=8
x=4
Option III
(2x+10)= (x+12)
2x-x=12-10
x=2

Isosceles triangles, are triangles where two of the lengths are the same so we can say that:
1. (3x+4)=(2x+10) 
2. (3x+4)=(x+12)
3. (2x+10)=(x+12)
One of these must be true. Solve as simultaneous equations.
1. x=6
2. x=4
3. x=2

He secknd step was the answer to them

A) for the n row: 22+(n-1)×6therefore,b) 100-22=78that means (n-1)×6=7878÷6=1313+1=1414th row has 100 seats