Answer:
B white blood cells
Step-by-step explanation:
If you used substitution to solve this equation, the answer would be (<span><span><span><span>76/21,</span></span></span></span><span>3/<span>7)</span></span>
Set x as Joe's (current) age, and y as Mary's age (current). We can start building equations; x = y - 2 + 10, or x = y + 8. Now, from the second statement, x - 2 = 2(y - 2). Substituting, we obtain y = 10, and x = 18.