I would approach word problems starting with the 'least' or lowest' and add on others in relation to it.
What is asked ?
What is given ?
relationship between her earning and those of (Robert and Alexis)
relationship between Robert and Alexis earning
Usually in any algebra word problem or expression, one is encouraged to start with an unknown, x. Then create a relationship between x and numbers to formulate an expression. In the example you mentioned, as many have commented already, there may be insufficient data since required...
Yes, to answer your question, the algebraic expression should be w + 3 + n where n = 1 as mentioned by Eugene P. Since they say 'whole number' it will haactions or decimals. Also they say 'the next ' whole numbers and since whole numbers are counted as 1, 2, 3 etc. next...
Usually in such algebraic equations, you need to see what pattern comes to mind. There are a number of formulae you should know by heart. Like the following :
(a+b)^2 = a^2 + 2ab + b^2
(a+b)(a-b) = a^2 - b^2
Similarly (a+b) ^3 = a^3 + 3a^2b + 3ab^2 +b^3