Probability =
(number of ways it can come out the way you want it to)
divided by
(total number of ways it can come out).
Total number of ways it can come out =
number of bottles in the cooler
= (10 + 15 + 13) = 38 .
Number of ways it can come out the way you want it to =
(soda + lemonade)
= (10 + 15) = 25 .
Probability of coming out the way you want it to =
25 / 38 = about 65.8 % .
Technically, this counts
82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105, 106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124, 125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142, 143,144,145,146,147,148,149,150,151,152