Answer:13 13/40 kg
Step-by-step explanation:
First box weigh 6 3/8kg
Second box weigh 7 2/5kg
Total weight = 6 3/8 +7 2/5
Total weight =(8x6+3)/8 + (5x7+2)/5
Total weight =51/8 +37/5
Total weight =(5x51+8x37)/40
Total weight =(255+296)/40
Total weight =551/40=13 13/40 kg