Stephanie adds pennies nickels and quarters to a scale until the masses combined coins and 75 grams each penny has a mass of 2.5 grams each peach court has a mass of 5.7 grams create an equation to model the situation where x is the number of pennies why is the number of nickels and z is the number of quarters that stephanie can put on the scale so that the mass of the combined coin is exactly 75 grams