Write and solve a system of equations to find the value of each variable can you please help

Find the x coordinate of the point.

Frank has a devised a formula for his catering business that calculates the number of meatballs he needs to prepare. the formula is m=4a+2c, where c=number of children; m=number of meatballs; a=number of adults. how many meatballs are required for a party of 10 adults and 5 children?

What is the value of -3/4 to the 4th power? -256/81 -81/256 81/256 256/81