Let x be pounds of apples, and y be pounds of peaches.
x+y= 165 ... total of pounds sold
1.75x+2.50y= 337.5 .... total of money earned
Solve this system:
x=165-y
1.75(165-y)+2.50y=337.5
288.75-1.75y+2.50y=337.5
0.75y=337.5-288.75
0.75y=48.75
y=48.75/0.75
y= 65
She sold 65 pounds of peaches