Solve for x: 15). x - 50 = 49 16). x - 125 = 375 17). x - 50 = -25 18). x - 90 = - 30 19). x - 197 = 0 20). x + 128 - 256 = 64 (two steps) 21). Chang has 43 comic books left in his collection. Last week he gave 10 of them to Anne and 5 to Matt. How many comic books did he start with? Let x be the number he started with. Write the algebraic equation: ____________________ and solve for x = _________