This one you can't really make a formula for or anything, but it's fairly simple to figure out, with a bit of guess and check. 14 is really close to 15, but that's bigger, so let's try a smaller number that would work. It has to be divisible by 2, because you've got a whole number that is 3 1/2 times the other number. (1/2 of a whole number means it's divisible by 2). 10 is divisible by 2, 10 ÷ 2 = 5 But, 10 x 3 = 30 which is much bigger than 14. So, we've got to start with a smaller number. Let's try something really small, like 4. We could try 2, but 2 x 3 = 6, which, even with 1/2 of 2, isn't nearly close to 14. Now, 4 x 3 = 12 That's quite close to 14. And 1/2 of 4 is 2. All we do now is add 12 to 2 and see if it works. 12 + 2 = 14 14 = 14 This one works. That means that Gina volunteered for 4 hours, because 3 1/2 x 4 = 14.
To find the area of a parallelogram you multiply the base times the height, or the length times the height. This is why you multiply 5x8 to get 40. The substitution could be 5 x 8 = X
