Answer:
[tex]Dave\ should\ buy\ 2735\ nails.[/tex]
Step-by-step explanation:
[tex]Number\ of\ nails=70\\\\Good\ nails=64\\\\percentage\ of\ good\ nails=\frac{good\ nails}{total\ nails}\times 100\\\\percentage\ of\ good\ nails=\frac{64}{70}\times 100\\\\percentage\ of\ good\ nails=91.42857\%\\\\Let\ for\ 2500\ good\ nails\ he\ has\ to\ buy\ x\ nails\\\\91.42857\%\ of\ x=2500\\\\\frac{91.42857}{100}\times x=2500\\\\x=\frac{2500}{0.9142857}=2734.375\\\\x\approx 2735[/tex]