There are 4/7 boys, so there are 3/7 girls.
Let the total number of children be x.
4/7x = 8
1/7x = 8 ÷ 4
1/7x = 2
3/7x = 2 x 3
3/7x = 6
There are 6 girls.
1. 3x - 2y = 8 Subtract 3x on both sides
-2y = 8 - 3x Divide by -2 on both sides to get y by itself
y = -4 + 3/2x
2. a + b / 3 = 5 Multiply 3 on both sides
a + b = 15 Subtract a on both sides to get b by itself
b = 15 - a
3. 12x - 4y = 20 Subtract -12x on both sides
-4y = 20 - 12x Divide -4 on both sides to get y by itself
y = -5 + 3x
4. y + 3 = -5(x - 2) Multiply -5 to (x-2)
y + 3 = -5x + 10 Subtract 3 on both sides to get y by itself
y = -5x + 7
I'm guessing you'd combine them. And the end equation would be
81x6y
