You multiply the numerator and denominator of 3/4 with 3 and multiply 1/3 with 4 on the bottom and top and after you get 36/144 you simplify it and you get 1/4 so thats your answer
We first have to use the second purchase to figure this out, if 4 bags of sand is $8. We have to divide 8 by 4, which we get $2. We use this to find the bags of pea gravel. Since you bought 3 bags, 3 times 2 is 6. We subtract 6 from 26 leading to 20 dollars. We also buy 5 bags of pea gravel so we have two numbers, 20 and 5. We divide 20 and 5 and we get 4 dollars for 1 bag of pea gravel. If this is not what you meant I apologise.