First we do the sum in brackets: -2.4-0.63=-3.03. (-.63 is the same as -0.63 and -2.4 is the same as -2.40.)
Next we multiply this by 1.8 which gives us -5.454, and finally -5.454 times -3.42=18.65268, because the minus signs multiplied together make plus so we don’t need a sign in front of the result. I’m assuming there is no operator between the bracket and 1.8, so multiplication is implied.