There are (3x-1) girls and (4x+2) boys in the school parade square. One child is selected at random. If the probability that the child is a girl 2/5, calculate

the prob = 2/5 is obtained from
(3x - 1)/((3x - 1) + (4x+2))
2/5=(3x - 1)/(7x + 1)
the multiply each by 5
2 = 5(3x - 1)/(7x + 1)
multiply each by (7x + 1)
2(7x + 1) = 5(3x - 1)
14 x + 2 = 15x - 5
calculate as it is
2 + 5 = 15x - 14x
7 = x

so we know now that x is 7
to proof it u can subs the x into the equation