Triangles with Algebra

Which of the following equations cannot be used to find the value of x?

• $2x+x=90$

• $2x=x+90$

• $2x+x+90=180$

Which of the following equations is the correct way to find the value of x?

• $51+2x+3+4x+8=180$

• $2x+3+4x+8=51$

• $2x+3+51=4x+8$

• $4x+8=90$

Find the value of x.

• 25

• 36

• 47

• 11

Find the value of x.

• 30.5

• 51

• 19.5

• 25

The triangle is an equilateral triangle. What is the value of n?

• 25.5

• 48

• 18

• 3