Two numbers total 77 and have a difference of 21. find the two numbers

So we can create two expressions to represent these.

X+Y=77

X-Y=21

we can use substitution or elimination

let's rearrange one of the equations.

let's make X-Y=21. let's move the y over!

X=y+21 now we can plug it in to the other equation!

y+21+y=77

2y+21=77

move 21 over ...

2y=56

y=28! just use this value to find X

use any equation you want.

X+28=77

X=49

two values are 49 and 28