Use distributive property to remove the parenthesis. Distributive property allows us to "distribute" or share the one outside the parenthesis to all term inside the parenthesis.
6(1R + 5) + 3R
= 6 × 1R + 6 × 5 + 3R
Then work on the multiplication
= 6 × 1R + 6 × 5 + 3R
= 6R + 30 + 3R
Add the one with variable R together
= 6R + 30 + 3R
= 9R + 30
This is the simplest expression