We have used equations and the equal sign to represent relationships and constraints in various situations. Not all relationships and constraints involve equality, however. 

In some situations, one quantity is, or needs to be, greater than or less than another. To describe these situations, we can use inequalities and symbols such as $<, \leq, >$, or $\geq$.

When working with inequalities, it helps to remember what the symbol means, in words. For example:

• $100 < a$ means “100 is less than $a$.” 
• $y \le 55$ means “$y$ is less than or equal to 55,” or "$y$ is not more than 55."
• $20 > 18$ means “20 is greater than 18.”
• $t \ge 40$ means “$t$ is greater than or equal to 40,” or "$t$ is at least 40."

These inequalities are fairly straightforward. Each inequality states the relationship between two numbers ($20>18$), or it describes the limit or boundary of a quantity in terms of a number (100<a></a></span>). </p> <p>Inequalities can also express relationships or constraints that are more complex. Here are some examples:</p> <div class="imgrid"> <div class="g--row"> <div class="g--column g--content g--three-fourth"> <ul> <li>The area of a rectangle, <span class="math">\(A, with a length of 4 meters and a width of $w$ meters is no more than 100 square meters.