An IV solution contains 135 mEq/L Na+, 45 mEq/L K+, and 12 mEq/L Ca2+. If HCO3- is the only anion in the solution what is its concentration in mEq/L?

I think the concentration in mEq/L is going to be 45

1. and 2. question: in which equation? or i don't understand you, 3. a), 4. c), 5. c), 6. b), 7. d), 8. d) if small number is underlined(behind symbol) , b) if big number is underlined(in front of symbol)9. what is underlined there? 10. c)