I need the answers I don’t understand it

Cara earns a base pay of $1800 per month at a car dealership plus a commission of 6% of her sales. what are caras total earning in a month in which she sells $40000 worth of merchandise

Clara solved the equation 7/3x = −2/3 as shown → 7/3x( 3/7 ) = −2/3 ( 3/7 ) x = −14 what is clara’s error?

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