y=0.8(300-0.7(300-y))

Solution for y=0.8(300-0.7(300-y)) equation:

Simplifying
y = 0.8(300 + -0.7(300 + -1y))
y = 0.8(300 + (300 * -0.7 + -1y * -0.7))
y = 0.8(300 + (-210 + 0.7y))

Combine like terms: 300 + -210 = 90
y = 0.8(90 + 0.7y)
y = (90 * 0.8 + 0.7y * 0.8)
y = (72 + 0.56y)

Solving
y = 72 + 0.56y

Solving for variable 'y'.

Move all terms containing y to the left, all other terms to the right.

Add '-0.56y' to each side of the equation.
y + -0.56y = 72 + 0.56y + -0.56y

Combine like terms: y + -0.56y = 0.44y
0.44y = 72 + 0.56y + -0.56y

Combine like terms: 0.56y + -0.56y = 0.00
0.44y = 72 + 0.00
0.44y = 72

Divide each side by '0.44'.
y = 163.6363636

Simplifying
y = 163.6363636