Answer:
575 boxes
Step-by-step explanation:
Let the total number of boxes = x
The farmer already loaded [tex]\dfrac25[/tex] of the boxes onto the truck.
Therefore, the remainder [tex]=1-\dfrac25=\dfrac35[/tex]
Since he needed to load 345 more boxes of tomatoes onto the truck.
[tex]\dfrac35 \times x =345\\3x=345\times5\\x=(345\times5) \div 3\\x=575[/tex]
The farmer had 575 boxes of tomatoes to load altogether.