Question

Can anyone help with grade 9 math?

Answer 1

`65/7\ g`

Explanation:

We can make two linear equations. Let `s` be the mass of a sphere and `c` be the mass of a cube, both in grams.

The left side of the mass tells us that
`5s + c = 65`
and
`s + 3c = 65`

We can take three times the first minus the second equation to get

`15s + 3c = 195`
`- s-3c = -65`

`14s = 130 implies s = 65/7`

If we want to check, we can find that `c = 2 * s = 130 / 7`. Plugging that into the above:

`5 * (65/7) + 130/7 = 7/7 * 65 = 65`
and
`(65/7) + 3 * (130/7) = 7/7 * 65 = 65`

as we hoped.