Because you are given the ingredients for one batch, and you want the ingredients for four batches, you can multiply all of the original quantities by 4 to find the answers.
1 1/2 × 4 To do this, first convert 1 1/2 into a mixed number by doing 1 × 2 = 2, and 2 + 1 = 3, which would be the numerator. This then gives you 3/2 × 4/1, which simplifies to 12/2, which means your answer is 6.
1 × 4 = 4
1 × 4 = 4
3 × 4 = 12
3/4 × 4 = 3 (you cancel out the "/4" because you're multiplying by 4)
