8. a) To find how many matches are used to make shape 9, you substitute 9 in as n, so your equation looks like m = (4 × 9) + 1 m = 36 + 1 m = 37 So the amount of matchsticks is 37
b) Now we can substitute in 21, but place it where m is, so we get: 21 = (4 × n) + 1 - 1 20 = 4 × n ÷ 4 5 = n So your answer is shape number 5.
9. You can write this out as an equation: (6 × l) + (8 × p) = 640 Because you know that each letter is 100, you can substitute 100 in for l and get (6 × 100) + (8 × p) = 640 600 + (8 × p) = 640 - 600 8 × p = 40 ÷ 8 p = 5 So each pen is 5g.