What is the value of r in: 1/7 (105+r) = 20

Use the distributive property.

1/7 (105 + r) = 20

15 + (1/7) r = 20

Then subtract each side of the equation by 15.

15 + (1/7) r = 20

(1/7) r = 5

Divide both sides by 1/7.

(1/7) r = 5

r = 35

So, the answer to this question is r is equal to 35.