total guests = 61
tamya's = t
brother = b
t = b + 19
t + b = 61
b + 19 + b = 61
2b + 19 = 61
2b = 61 - 19
2b = 42
b = 42/2
b = 21
t = 21 + 19
t = 40
Tamya invited 40 guests
her brother invited 21 guests
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