Question 83747
{{{((5y^6)(3y) - (y^4)(8y^3))}}} 
{{{((15y^7) - (8^7))}}}[multiply coefficients and exponents; to multiply exponents, add]
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{{{(7y^7)}}} [subtract coefficients since the exponents are the same; if the exponents were different, you could not subtract their coefficient]