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Andrew has 20 more goldfish than Todd. Together they have 70 goldfish.

How many goldfish does each boy have?

Step-by-step explanation:

We can let "a" stand for the number of goldfish Andrew has. Then the number Todd has is (70-a). We are told the difference is ...

  a - (70-a) = 20

  2a = 90 . . . . . . .  .collect terms, add 70

  a = 45

  70-a = 25

Andrew has 45 goldfish; Todd has 25.

Comment on the problem

I call this a "sum and difference" problem. You are given the total of two counts, and also their difference. If you were paying attention to the above solution, you see that the larger of the counts is (70+20)/2, half the sum of the given numbers. This is generically true of all sum and difference problems.

Knowing this, you can work most of these problems in your head.

so a parallelogram is just like a square base times height. multiply 40 and 39 to get 1560 inches.

a triangle is base times height divided by two. so multiply 7.9 and 5 and then divide it by 2 to get 19.75inches.

the kite can be split into two separate triangles and added together to get the total area. 30 x 4 /2 which equals 60. make sure to double it for the two triangles making 120.