The expression equivalent to the total distance Joe is training for the triathlon is x² + 3x + 5.
The distance she runs is expressed as 2x miles.
The distance she cycles is expressed as x² + 7 miles.
The distance she swims is expressed as x - 2 miles.
All these expressions are linear equations with one variable. Linear equations are expressions with highest power of the variable is 1.
The total distance can be obtained by summation of the three expressions, that is
2x + (x² + 7) + (x - 2) = x² + 3x + 5
To know more on linear equations with one variable
https://brainly.com/question/2756237
#SPJ4