If we know that Pedro bought 1

pounds of red sand, and 5

pounds of brown sand, and they both cost $4.60, then we just have to add the individual amounts of sand, since they cost the same.

So Pedro bought

lbs of sand overall. Now, we just need to multiply the cost per pound by the total amount of sand he bought.

Pedro spent $31.05 on sand, which is answer choice B.
Hope that helped =)