Question

If 5kg more then 3 times Mac's Mass is decreased by twice his mass, the result is 60kg. What's Mac's Mass?

Answer 1

Mac's Mass is `55` kg.

Explanation:

Let `m` be Mac's Mass
and convert the description a bit at a time into algebraic form:

5kg more than 3 times `color(green)("Mac's Mass")` is decreased by twice `color(green)("his mass")`, the result is 60kg
`rArr`5kg more than 3 times `color(green)(m)` is decreased by twice `color(green)(m)`, the result is 60kg

5kg more than `color(red)(3" times "m)` is decreased by `color(blue)(" twice "m)`, the result is 60kg
`rArr`5kg more than `color(red)(3m)` is decreased by `color(blue)(2m)`, the result is 60kg

`color(green)(5"kg more than "3m)` is decreased by `2m`, the result is 60kg
`rArr` `color(green)(5+3m)` is decreased by `2m`, the result is 60kg

`color(red)((5+3m)" is decreased by "2m)`, the result is 60kg
`rArr`
`color(red)((5+3m)-2m)`, the result is 60kg

`((5+3m)-2m)` `color(blue)(" the result is "60"kg")`
`rArr` `((5+3m)-2m)` `color(blue)(=60"kg")`

So we have:
`(5+3m)-2m = 60`

Combining the `m` terms on the left side:
`5+m = 60`

Subtracting `5` from both sides:
`m = 55`