# Chapter 2 - Section 2.5 - An Introduction to Problem Solving - Exercise Set: 16

$x=11$

#### Work Step by Step

Let x = the unknown number Then "the sum of 5 and a number" means $5+x$ "3 times the sum" means $3(5+x)$ Thus, the equation that represents the situation is: $3(5+x)=48$ Use the distributive property to simplify. $(3\times5)+3x=48$ $15+3x=48$ Use the addition property of equality to subtract 15 from both sides of the equation. $15+3x-15=48-15$ $3x=33$ Use the multiplication property of equality to divide both sides of the equation by 3. $3x\div3=33\div3$ $x=11$

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