At a local store, kelly and martin bought some notebooks and pencils. kelly bought 4 notebooks and 25 pencils for 16.71. martin bought 6 notebooks and 20 pencils for 21.74 what is the cost of 1 notebook and 5 pencils

Let n = cost of 1 notebook
Let p = cost of 1 pencil

Then,

3n + 4p = 8.5
5n + 8p = 14.5

You can solve for one variable in terms of the other and then substitute into the remaining equation.

3n + 4p = 8.5
+ 5n + 8p = 14.5

Multiply the top equation by -2 so that the p-containing terms cancel each other out:

-2(3n + 4p = 8.5)
+ 5n + 8p = 14.5
-n + 0 = -2.5

So after dividing both sides by -1, we see that n = $2.5. Plugging into the first equation gives p = $0.25.

3n + 4p = 8.5
5n + 8p = 14.5