Question

B

(5x)
By the
(x + 10)
m/A+m/B+m/C= 180°. Using the
the sum of the angles in a triangle is equal to 180°. Therefore,
(5x) +90° + (x+10) = 180°. To
6x = 80. Then,
solve for x, first combine like terms to get 6x + 100 = 180. Using the
using the division property of equality, x= 13. To find the measure of angle A, use the substitution property to get
m/A= 5(13). Finally, simplifying the expression gets m/A=663*.

Answer 1

Let a triangle ABC and draw a line 1 throug

B

3

:: BC //

1 and AB and AC are transversals on it. angle4= angle2... (i)

(Alternate angles)

and angle 5 = angle3. (ii)

(Alternate angles)

Adding equations (i) and (ii), we get angle 4 + angle5= angle2+ angle3 angle 1 + angle4+ angle5= angle1+ angle2+

Add angle 1 on both sides.

angle3... (ii)

angle1+ angle4+ angle 5 = 180 deg

(1 is a straight line)

From (iii), angle1+ angle2+ angle 3 = 180 deg

Hence, sum of angles of a triangle is 180°.