ANSWER: a=12 b=15
Explanation: (look at work below)
4a + 1b = 63 (eq1)
5a + 3b = 105 (eq2)
-12a + -3b = -189 (subt. eq1 from eq2)
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-7a = -84
a = 12
4(12) + 1b = 63 (plug in the a value)
48 + 1b = 63
b = 15
I think you got confused with the 50 and 90.
Read my NOTE there it will surely help you answering other questions like this
Im not sure, but i think it is the last option or 24-2d
Well there are 33 total people in the class, so the chance of drawing a boy's name is