It is given that,
[tex]\begin{gathered} Area\text{ = 48 m}^{2\text{ }} \\ Height\text{ = 12 m} \\ Base\text{ = x} \end{gathered}[/tex]Area of the triangle is calculated as,
[tex]\begin{gathered} Area\text{ = }\frac{1}{2}\text{ }\times\text{ Base }\times\text{ Height} \\ 48\text{ = }\frac{1}{2}\text{ }\times\text{ x }\times\text{ 12} \\ x\text{ = }\frac{48\times2}{12} \\ x\text{ = 8 m } \end{gathered}[/tex]Thus the base of the given right angled triangle is 8 m.