counting problem

Johnny has 76 solid-colored disks that are either red, green, or blue. He lines them up on the floor and finds that there are 4 more red disks that green and 6 more green disks than blue. How many red disks does he have?

Not sure how they're getting 30?

Quote:

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Originally Posted by mjoshua

Johnny has 76 solid-colored disks that are either red, green, or blue. He lines them up on the floor and finds that there are 4 more red disks that green and 6 more green disks than blue. How many red disks does he have?

Not sure how they're getting 30?

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let r= Red disks
g= green disks
and b = blue disks.

then

there are 4 more red disks that green means:

6 more green disks than blue means:

from the above equation,you can also write

so

or,

that gives you

and you know that

you can also find out how many blue disks are there.. add the numbers up and you should get 76