For this one I'm going to assume that 4 7a means 4 * 7a...
(8 + 7a) + 4 * 7a =
8 + 7a + 28a =
8 + 35a
If I read it wrong and 4 7a is actually 47a then...
(8 + 7a) + 47a =
8 + 54a =
2(4 + 27a)
You have 32 tiles, you use 15 tiles, how many tiles are left?
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