Please help me with my math please

What is the simplified form of 7 √x • 7 √x • 7 √x • 7 √x?

Asystem of equations has 1 solution.if 4x-y=5 is one of the equations , which could be the other equation ?

Circle a has a diameter of 7 inches, a circumference of 21.98 inches, and an area of 38.465 square inches. the diameter of circle b is 6 inches, the circumference is 18.84 inches, and the area is 28.26 square inches. part a: using the formula for circumference, solve for the value of pi for each circle. (4 points) part b: use the formula for area and solve for the value of pi for each circle. (4 points)