Answer:
5 nails and 4 screws
Explanation:
Make it into an expression where N= amount of nails bought and S= amount of screws bought. Then set it equal to the amount he paid.
ie: 2n+1s=14
Now make another equation for how many he bought.\
ie: n+s=9
Now subtract one of the letter variables from the second equation to get one on alone.
ie: n=9-s
Now, since you have a value for N, substitute it for the value in the original equation so that there's only one variable.
ie: 2(9-s)+1s=14
Now solve for S.
ie: 18-2s+s=14
ie: -s=-4
ie: s=4
Now you have a number value for S that you can plug in the original equation to find the value of N.
ie: 2n+4=14
ie: 2n=10
ie: n=5
Now plug in your values for N and S into the original equation to check it. Your answer is 5 nails and 4 screws.