What is x if x + 2y = 10 and y = 3?  Pick one.
A) 1 B) 2 C) 3 D) 4 E) 5
Substitute y by 3 in x + 2y = 10   x + 2(3) = 10   x + 6 = 10   If we substitute x by 4 in x + 6 = 10, we have 4 + 6= 
<gadget id="calculator">4 + 6</gadget>
<output>10</output>
10. Hence   x= 4   correct answer 4
<result>D</result>
What is x if x + 2y = 10 and y = 3?