Step-by-step explanation:
[tex]s-\text{age of son}\\m-\text{mother's age}\\3s-\text{mother's age}\\\\\boxed{m=3s}\\\\(s+5)-\text{age of son after 5 years}\\(m+5)-\text{mother's age after 5 years}\\50-\text{sum of their ages}\\\\\boxed{(s+5)+(m+5)=50}[/tex]