Question 28514
Let the man have purchased X tools
Total value = $50,000
so each tool cost {{{50000/X}}}

If he had bought 50 more tools
X+50
Per piece cost would be {{{50000/(X+50)}}}
This is less by $20 per piece
i.e. {{{(50000/X) - 50000/(X+50) = 20}}}

Can you solve from here?