I need help with this question and could you please explain why

B, angle one is complementary to angle five and angles five and six are supplementary to each other. so if angle 5&6 are supp. then they equal 180°, so angle six is 100, so 180-100= 80°, so angle five is 80°, and since 5&1 are comp. angle one is also 80°

Step 1: 6x-10=1; step 2: 6x=11