6x-8=4x i need the answer to solve for x

Which value of c would make he following expression completely factored? 8x+cy

With this one. will mark brainliest

Hillel is juggling flaming torches to raise money for charity. his initial appearance raises $500\$500 $500 , and he raises $15\$15 $15 for each minute of juggling performance. the amount rr r of money hillel raises is a function of tt t , the length of his performance in minutes. write the function's formula.