Answer:
[tex]\large\boxed{7\dfrac{8}{9}+3.1=10\dfrac{89}{90}}[/tex]
Step-by-step explanation:
[tex]\text{Convert the decimal to the fraction:}\\\\3.1=\dfrac{31}{10}=3\dfrac{1}{10}\\\\7\dfrac{8}{9}+3.1=7\dfrac{8}{9}+3\dfrac{1}{10}\\\\\text{The common denominator is 90.}\\90=9\cdot10\\\\7\dfrac{8}{9}=7\dfrac{8\cdot10}{9\cdot10}=7\dfrac{80}{90}\\\\3\dfrac{1}{10}=3\dfrac{1\cdot9}{10\cdot9}=3\dfrac{9}{90}\\\\\\7\dfrac{8}{9}+3.1=7\dfrac{80}{90}+3\dfrac{9}{90}=(7+3)+\dfrac{80+9}{90}=10\dfrac{89}{90}[/tex]
