If I understood that question correctly, then I believe the answer is 3(3)+2(8). An expression is unlike an equation because it doesn't include the answer. 1+1 is an expression; 1+1=2 is an equation. If you wanted an expression for "triple three then add double eight," then write out 3(3), or 3*3, adding (+), 2(8), or 2*8.
Hope that helped.