It is -11x + 24 because you multiply the numbers in the parentheses by 3 then collect like terms 10x +24 - 21x then you do 10x minus 24x and you get -11x+24
Answer:

Step-by-step explanation:
To solve this question, we will first expand the expression using the distributive rule: 
Therefore:

Simplify:

Add up like terms:

Vertex angle = x
1 base angle = 1/2x - 8
180-x = (1/2x-8)x2
180-x = x-16
196-x = x
196 = 2x
x=98
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