HELP ME PLZZZ ASAP! Tyler’s work is incorrect. Explain the error he made.

Tyler is simplifying the expression 6 − 2x + 5 + 4x. Here is his work:
6 − 2 + 5 + 4
(6−2) + (5+4)
4 + 9
13

In trapezoid efgh, m∠hef=(4x2+16)∘ and m∠gfe=(5x2+12)∘. find the value of x so that efgh is isosceles.

The brain volumes (cm cubed) of 50 brains vary from a low of 904 cm cubed to a high of 1488 cm cubed. use the range rule of thumb to estimate the standard deviation s and compare the result to the exact standard deviation of 175.5 cm cubed, assuming the estimate is accurate if it is within 15 cm cubed

What is the radical expression that is equivalent to the expression 27 1 over 5?