Answers
1. x=7
2. x=6
3. x=9
4. x=8
Explanations
1. This is an isosceles triangle because two angles are congruent. This also means the two sides are the same. This means 7 = x.
2. This is an equilateral triangle because all the angles are the same. Therefore, all sides are also the same. So x = 6.
3. This is also an equilateral triangle. We know this because all sides are the same. So from this we know that x-3 = 6. Solve the equation, and you'll find that x = 3.
4. This is also an isosceles triangle, because two of the angles are congruent. This means 2x-9 = 7. Solve this equation; x=8