We are given a parallelogram, with angles <1, (3m+20)° and 5m°.
Please note: The sum of adjacent angles of a parallelogram are supplementary that is sum equal to 180° and opposite angles are equal.
Therefore,
(3m+20)° + 5m° = 180° and < 1 = (3m+20)°
Solving equation (3m+20)° + 5m° = 180° for m.
3m +20 +5m = 180
Combining like terms, we get
8m +20 = 180.
Subtracting 20 from both sides, we get
8m +20-20 = 180-20
8m = 160
Dividing both sides by 8, we get
8m/8 = 160/8
m = 20
Plugging m=20 in 3m+20, we get
3(20)+20 = 60+20 = 80°
Therefore, <1 = (3m+20)° = 80°.
So, <1 =80°, 3rd option is correct option.