I am on a low carb diet, every other day i do 40 minutes on a cross trainer and 30 minutes on a bike... will i loose much weight this way? or will it tone?

No way to tell: It depends upon your total caloric expenditure versus your intake. It takes 3, 500 calories to gain or lose a pound. Calculate your intake minus expenditure -- if the number is negative, divide 3500 by that number and the result is the number of days it will take to lose a pound. Focused exercise will, in general, help to tone you up, but there are many other variables.