Answer:
x = (4 + 2√34)/10, x = (4 - 2√34)/10
Step-by-step explanation:
5x² - 4x = 6
Subtract: 5x² - 4x - 6 = 0
Quadratic formula: x = (4 ± √(16 - 4*5*(-6)))/10
Multiply: x = (4 ± √(16 + 120))/10
Simplify: x = (4 ± 2√34)/10
Let p be the prize of a pen and m the prize of a mechanical pencils. If you buy six pens and one mechanical pencil, you spend 6p+m. We know that this equals 9, because you get 1$ change from a 10$ bill.
Similarly, if you buy four pens and two mechanical pencils, you spend 4p+2m, which is 8$, because now you get a $2 change. Put these equation together in a system:

Now, if you multiply the first equation by 2, the system becomes

Subtract the second equation from the first:

Plug this value into the first equation to get

It’s 8^6, you’re correct :)
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