Please help!! I'm stuck on this question

Question

A builder discovers that a load of bricks is twice as heavy as a load of sticks. The total weight of 4 loads of bricks and 4 loads of sticks is 771 kilograms.

What is the total weight of 1 load of bricks and 3 loads of sticks?

1 load of bricks and 3 loads of sticks weighs  kg.

Answer 1

B=2S

4B+4S = 771

4(2S) + 4S = 771

8S + 4S = 771

12S = 771

S = 771/12 = 257/4 = 64.25 kilos per load of sticks

B =2S= 128.5 kilos per load of bricks

1B + 3S = 128.5 + 3(64.25) = 128.5 + 192.75 = 321.25 kilos for 1 load of bricks and 3 loads of sticks