Find the value of X need help soonnn

Answer soon(fast) 15 pts-brainliest? for right answer with small explination a restaurant catered a party for 40 people. a child’s dinner (c) cost $11 and an adult’s dinner (a) cost $20. the total cost of the dinner was $728. how many children and adults were at the party? use the table to guess and check.(i couldn't get the graph onto the question)                                8 children and 32 adults9 children and 31 adults10 children and 30 adults12 children and 28 adults

Solve the system of equations y= 3/2 - 1, -x+ y =-3

Afrequency table of grades has five classes (a, b, c, d, f) with frequencies of 3, 13, 14, 5, and 3 respectively. using percentages, what are the relative frequencies of the five classes?