How many tennis balls do you need to balance to scale

What is the value of x in the equation 2(x-4) = 4(2x + 1)?

Arestaurant chef made 1 1/2 jars of pasta sauce. each serving of pasta requires 1/2 of a jar of sauce. how many servings of pasta will the chef be bale to prepare using the sauce?

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827