13. There are several red and white balls in a bag. If each time 2 red balls and 3 white balls are taken out, when there are no white balls left in the bag, there are still 18 red balls left; if each time 5 red balls and 3 white balls are taken out, when there are no red balls left in the bag, there are still 18 white balls left. How many red balls are there in the bag? $\qquad$
【Analysis】Consider 3 white balls as 1 group,  
if 2 red balls are allocated to each group, then there are 18 more red balls,  
if 5 red balls are allocated to each group, then there are $18 \div 3 \times 5=30$ fewer red balls,  

Therefore, the number of white balls is $(1) 8+30 \div 5-2=16$ groups, and the number of red balls is $16 \times 2+18=50$.