A man selling computer parts realizes that when

he sells 16 computer parts, his earning is $1700.

When he sells 56 computer parts, his earning is

$4300. What will the earning be if the man sells 30

computers parts?

The seller must charge a one-time fee:

y=one-time fee

x=profit for each computer part

we would have to compute the following system of equations:

y+16x=$1700

y+56x=$4300

We can solve this system by substitution method

y+16x=$1700 ⇒y=$1700-16x

y+56x=$4300

($1700-16x) + 56x=$4300

40x=$4300-$1700

40x=$2600

x=$2600/40

x=$65

we find out the value of "y"

y=$1700-16x

y=$1700-16 ($65)

y=$1700-$1040

y=$660

if we would sell 30 computers parts the profit would be: 30x+y

profit if the man sells 30 computers parts=30 ($65) + $660=$2610

answer: his earning will be $2610