4x + 4y=4^8
x+y=20
y+y=?

solution please.

and for the last one too

What is the difference between regular convex and concave polygons

Donald has x twenty-dollar bills and 11 ten-dollar bill. how much money does donald have? write your answer as an expression.

Hurrya vegetable garden and a surrounding path are shaped like a square that together are 11ft wide. the path is 2ft wide if one bag of gravel covers 9 square feet how many bags are needed to cover the path