# In a triangle, the first side is x cm larger than the second and 5 cm less than the third side.

**In a triangle, the first side is x cm larger than the second and 5 cm less than the third side. The length of the second side is 10 cm. Write it as an expression: What is the perimeter of the triangle.**

Find what is the length of the first side of this triangle.

From the condition of the problem it is known that the first side of this triangle is x cm larger than the second, and the length of the second side is 10 cm, therefore, the length of the first side of this triangle is x + 10 cm.

Find what is the length of the third side of this triangle.

According to the condition of the problem, the first side of this triangle is 5 cm less than its third side, therefore, the length of the third side of this triangle is x + 10 + 5 = x + 15 cm.

Then the perimeter of this triangle is x + 10 + 10 + x + 15 = 2x + 35 cm.

Answer: the perimeter of this triangle is 2x + 35 cm.