The value of m when l is 73 can be found by substituting the 73 for l in l=24+3.5m and then solving for m. The resulting equation is 73=24+3.5m; subtracting 24 from each side gives 49=3.5m. Then, dividing each side of 49=3.5m by 3.5 gives 14=m. Therefore, when l is 73, m is 14. Choice B is incorrect and may result from adding 24 to 73 , instead of subtracting 24 from 73, when solving 73=24+3.5m. Choice C is incorrect because 73 is the given value for l, not for m. Choice D is incorrect and may result from substituting 73 for m, instead of for l, in the equation l=24+3.5m.