Step 1: Recall the two tags:
The
<sub> tag lowers the text below the normal line. This is called a subscript. The
<sup> tag raises the text above the normal line. This is called a superscript.
Step 2: Statement I: subscripts:
In H2SO4 the numbers 2 and 4 are written low, so each one is wrapped in
<sub>. The letters stay normal.
The chemical formula for Sulfuric Acid is H<sub>2</sub>SO<sub>4</sub>.
Step 3: Statement II: superscripts:
In a2 + b2 = c2 the small 2 is a power, so it is written high. Each 2 is wrapped in
<sup>.
The Pythagorean theorem is a<sup>2</sup> + b<sup>2</sup> = c<sup>2</sup>.
Step 4: Statement III: subscripts again:
In (X1, Y1) the 1 sits low after each letter, so each 1 is wrapped in
<sub>.
The coordinates are represented as (X<sub>1</sub>, Y<sub>1</sub>).
Step 5: Put the three lines on the page:
Each statement is a separate paragraph, so we place each one in a
<p> tag.
<p>The chemical formula for Sulfuric Acid is H<sub>2</sub>SO<sub>4</sub>.</p>
<p>The Pythagorean theorem is a<sup>2</sup> + b<sup>2</sup> = c<sup>2</sup>.</p>
<p>The coordinates are represented as (X<sub>1</sub>, Y<sub>1</sub>).</p>
Final Answer:
Use the sub tag for the low numbers in statements I and III and the sup tag for the powers in statement II.
\[ \boxed{\text{sub for H2SO4 and X1, Y1; sup for the powers in a2 + b2 = c2}} \]