Explain the the mistake in the student work

How do you use the elimination method for this question? explain, because i really want to understand!

Carli has 90 apps on her phone. braylen has half the amount of apps as theiss. if carli has three timesthe amount of apps as theiss, how many apps does braylen have? let b represent the number of braylen's apps and t represent the number of theiss's apps.

Find the product with the exponent in simplest form. then, identify the values of x and y. 6 ^ 1/ 3 • 6 ^ 1 /4 = 6 ^ x/ y