Aman 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

his earning will be $2610