\( \begin{array}{lll}\begin{array}{lll}\text { (a) } 3 g=6.3\end{array} \\ \begin{array}{ll}\text { (b) } 5 x=12+18\end{array} \\ & \text { (c) } 2(a+2 a)=90\end{array} \)

In the realm of algebra, this set of equations showcases the beauty of solving for unknowns. We're essentially peeling back the layers of a mathematical mystery! For (a), we can divide both sides by 3 to find \( g = 2.1 \). In (b), add up the right side to simplify: \( 5x = 30 \) thus \( x = 6 \). For (c), simplify \( 2(a + 2a) = 90 \) which leads to \( 2(3a) = 90 \); then divide by 6 to find \( a = 15 \). Understanding foundational concepts like balancing equations helps illuminate the path to finding solutions. Remember, every variable you isolate is like unlocking a treasure chest full of valuable insights that could lead you to more complex mathematical conquests in the future!