(1) O=orange, P=peach carbohydrate content in grams.
P=O-5, so if P=10, 10=O-5, O=15g carbohydrate in the orange.
(2) G=number of grapefruits. C=amount in mg of vit C in a whole grapefruit, so G grapefruits contain GC mg of vit C. When G=½, ½C=47, C=2×47=94mg. A whole grapefruit contains about 94mg of vitamin C.
(3) S=amount of skim milk in litres. Mass of Ca in 1L=1280mg, so mass of Ca in S litres=1280S. When S=250mL=250/1000=0.25L, mass of Ca=0.25×1280=320mg.
(4) B=amount of fibre in grams in a 250-mL serving of baked beans. P=amount of fibre in one 85g serving of pasta. 2P=amount of fibre in two servings of pasta. B=2P+1. When B=11g, 11=2P+1, 10=2P, so P=10/2=5g of fibre in one 85g serving of pasta.
(5) A=mass (mg) of K in apple. B=mass (mg) of K in banana.
A=⅓B+10. When A=160, 160=⅓B+10, 150=⅓B, B=3×150=450mg of potassium in one banana.
(6) S=amount of protein (grams) in one serving. 3S=36g, S=36/3=12g.
One serving = A+Y where A=amount of protein in 250ml of dried apricots and Y=amount of protein in 125g of yogurt.
S=A+Y. When S=12 and Y=7, 12=A+7, A=5g of protein in 250mL of dried apricots.
Please try question 2 yourself by researching the internet for nutritional information and then using the above questions and answers to devise your problems.