An algebraic expression of the form $a + bx$ has the value of $15$ when $x = 2$ and the value of $3$ when $x = 5$. Calculate $a + b$.
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<|im_start|>user
An algebraic expression of the form $a + bx$ has the value of $15$ when $x = 2$ and the value of $3$ when $x = 5$. Calculate $a + b$.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
19
An algebraic expression of the form $a + bx$ has the value of $15$ when $x = 2$ and the value of $3$ when $x = 5$. Calculate $a + b$.
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