How to Find a Missing Angle in a Triangle

Step-by-step solution

1. Write the angle sum rule.

   $$65^\circ + 48^\circ + x = 180^\circ$$

   Why: The three angles inside a triangle always add to 180 degrees.

2. Add the two known angles.

   $$113^\circ + x = 180^\circ$$

   Why: 65 plus 48 is 113.

3. Subtract 113 from 180.

   $$x = 67^\circ$$

   Why: The unknown angle is the remainder.

Practice problems

Use the same method. Work each problem on paper, then open the answer to check.

1. 1

   $90^\circ,\ 45^\circ,\ x$

   Show answer

   $x = 45^\circ$

2. 2

   $60^\circ,\ 60^\circ,\ x$

   Show answer

   $x = 60^\circ$

3. 3

   $100^\circ,\ 35^\circ,\ x$

   Show answer

   $x = 45^\circ$

4. 4

   $72^\circ,\ 29^\circ,\ x$

   Show answer

   $x = 79^\circ$

5. 5

   $55^\circ,\ 55^\circ,\ x$

   Show answer

   $x = 70^\circ$