15 is coefficient, a is a variable, 2 and -7 are like terms, 15a is a term and 2 and 7 are constants.
Volume is measured of the objects which are three-dimensional .. And square is just a shape , hence it doesn't have any formula for volume .
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If you were tryna ask about cube , the formula for cube is s^3
Where s is the side of the cube
1.) 6x-8y=18, 2x+8y=6 → Multiplication property of equality
2.) 8x=24 → Addition property of equality
3.) x=3 → Division property of equality
4.) 3(3)-4y=9 → Substitution property of equality
5.) 9-4y=9 → Simplify
6.) -4y=0 → Subtraction property of equality
7.) y=0 → Division property of equality
