Take the fouth square root of both sides
![\sqrt[4]{{x}^{4} } = \sqrt[4]{24}](https://tex.z-dn.net/?f=%20%5Csqrt%5B4%5D%7B%7Bx%7D%5E%7B4%7D%20%7D%20%20%3D%20%20%5Csqrt%5B4%5D%7B24%7D%20)
so
![x = \sqrt[4]{24} \: or \: x = - \sqrt[4]{24}](https://tex.z-dn.net/?f=x%20%3D%20%20%5Csqrt%5B4%5D%7B24%7D%20%20%5C%3A%20or%20%5C%3A%20%20x%20%3D%20%20-%20%20%5Csqrt%5B4%5D%7B24%7D%20)
You divide the 15x by the 124. I know it sounds weird because you'll get a decimal, but that is what you are supposed to do because 124 is not a factor of 5.
Answer:
She wrote a 4 instead of a 3.
There are only 3 numbers that are greater than 7. They are 8, 9, and 10. Mariah must have include 7 in her list. That is how she got 4 instead of 3.
