We need to distribute the parenthesis before we do anything. 0.02(x+20)=0.02x+0.4; now let's put this into the equation.
2.4+0.02x+0.4-4.8=-9; this is all about making sure we get x on one side, isolated. We need to add all the like terms.
0.02x-2=-9; let's add 2 to both sides. 0.02x=-7; let's divide each side by 0.02 so that we can have x by itself. x=-350; let's plug -350 in as in the original equation to make sure that is our answer.
2.4+0.02(-350+20)-4.8=-9; let's add the parenthesis. 2.4+0.02(-330)-4.8=-9; let's multiply. 2.4-6.6-4.8=-9; let's subtract. 2.4-6.6=-4.2-4.8=-9
So, x=-350.