(84.911789x) + (86.909183(1 - x)) = 85.468 --> Multiply out the brackets
84.911789x + 86.909183 - 86.909183x = 85.468 --> Subtract the bold part from both sides
84.911789x - 86.909183x = - 1.441183 --> Simplify the left side of the equation
- 1.997394x = - 1.441183 --> Divide both sides by the bold part to get x
x = 0.721532 --> Convert to percentage
= 72% (2.s.f.)
