Chapter 5 - Section 5.3 - Special Products - Exercise Set - Page 368: 72

$80y^2-10y-15$

Using $(a+b)(c+d)=ab+ad+bc+bd$ or the FOIL Method, the product of the given expression, $ (8y+3)(10y-5) ,$ is \begin{array}{l}\require{cancel} 8y(10y)+8y(-5)+3(10y)+3(-5) \\\\= 80y^2-40y+30y-15 \\\\= 80y^2-10y-15 .\end{array}