Subjuctive or indicative mood?

Hi, everyone,

If you had to write a math equation, you probably wouldn’t write, “Twenty-eight plus fourteen equals forty-two.” It would take too long to write and it would be hard to read quickly. You would write, “28 + 14 = 42.” Chemistry is the same way. Chemists have to write chemical equations all the time, and it would take too long to write and read if they had to spell everything out. So chemists use symbols, just like we do in math. A chemical formula lists all the elements that form each molecule and uses a small number to the bottom right of an element’s symbol to stand for the number of atoms of that element. For example, the chemical formula for water is H2O. That tells us that a water molecule is made up of two hydrogen (“H” and “2”) atoms and one oxygen (“O”) atom.

* source;

https://books.google.co.kr/books?id=6CT0BQAAQBAJ&pg=PA9&lpg=PA9&dq=%22if+you+had+to+write+a+math+equation%22&source=bl&ots=69lAubXies&sig=ACfU3U2ChJ0im8dSb8zvTWU963l6foUerA&hl=ko&sa=X&ved=2ahUKEwjUp43FoIjwAhVGUd4KHUtrBuEQ6AEwBnoECAsQAg#v=onepage&q=%22if%20you%20had%20to%20write%20a%20math%20equation%22&f=false

In the quotation the first sentence - If you had to write a math equation, you probably wouldn’t write, “Twenty-eight plus fourteen equals forty-two.”, I'm inclined it is in an indicative mood, since I think, the "would" is not for subjunctive mood but for writer's strong assumption, and also the main clause seems to be factual.

However, I will much appreciate;1

1. if you kindly explain me in case of my wrong assumption.

2. if it is in a indicative mood, why this writer used "had to" at the place of "have to"?

3. if it is in a indicative mood, the "would" is for the present or past tense?
Best RGDS,