Let T be the number of toys Joel’s sister donated.
Joel donated twice as many toys, so he donated 2T toys.
Joel’s friends donated 18 + 42 + 2 + 13 = <<18+42+2+13=75>>75 toys.
In all, Joel collected T + 2T + 75 = 3T + 75 = 108 toys.
Joel and his sister donated 3T = 108 - 75 = 33 toys together.
Therefore, T = 33 / 3 = <<33/3=11>>11 toys were his sister’s.
Thus, 2T = 2 * 11 = <<2*11=22>>22 toys were Joel’s.
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