<span>it all looks confusing when we try to juggle with all those numbers in the head. The problem can be solved systematically by constructing a contingency table.
</span>role/gender B G total
speaking...... 4 4 8
<span> silent............ 4 8 12
total............. 8 12 20
</span>Probability of a child having a speaking part is therefore
(4+4)/20=8/20=2/5
a. 2/5
3x+y=17
=> 3x=17-y
Again, x+3y=-1
=> 3y= -1-x
now, 3x+3y= (17-y)+(-1-x)
= 17-y-1-x
= 16-x-y
Don't know if it's right, but do let me know! use percentage to visualise your workings. :)
4³/₄ × 1¹/₂
¹⁹/₄ × ³/₂
⁵⁷/₈
7¹/₈