At a stall, the ratio of watermelons to coconuts was 8:13. After Kate bought two-thirds of the coconuts, there was a total of 111 watermelons and coconuts left at the stall. How many fruits were there at first?
Number of watermelons --- 8x
number of cocos ---- 13x
2/3 of cocos bought leaving (1/3)(13x) or 13x/3 cocos
8x + 13x/3 = 111
24x + 13x = 333
37x = 333
x = 9
original: 72 watermelons, 117 cocos
total fruits = 8x+13x = 21x = 189