Question

Help me pls u need it

Answer 1

Call the number of blue jays
`b` and the number of robins
`r`

We are told there are twice as may robins as blue jays:

`r=2b`
and, there are 21 birds in total:

`r+b=21`
thus, by substitution:

`2b+b=21`
combine like terms:

`3b=21`
solve for
`b`:

`b=7`
back substitute:

`r=2(7)`

`r=14`

There are 7 blue jays and 14 robins.