Multiplication is usually not used between letters

Hello, in this video we will study the branch of mathematics called algebra. First of all, you need to know arithmetic signs. In arithmetic, we use addition, subtraction, division and multiplication. For example: 2+5=7; 7-2=5; 4*5=20; 36:6=6. Usually, numbers can be interchanged in addition and multiplication signs. The letter "X" is often used for an unknown number. When do we use the unknown? For example, 2+4=X: we perform the addition sign and use the letter "X" because the result is unknown to us. Also, any arithmetic sign involving an unknown is called an equation. An equation is a mathematical statement in which two things are equal. One of the main goals of algebra is to determine what the unknown values ​​in equations are. The 2+4=X equation I wrote is the simplest. We see that X is equal to 6 here. Basically the same symbol (or letter) is used in the equation. Any number of symbols (or letters) can be included in the equation. The same symbol (or letter) in the equation

The difficulty level of this equation is easily compared to other equations. You can also put letters instead of numbers in the equation. For example: a+b=5
This is more complicated than the previous one. Because here a=2; b=3; can be. Again, a=3; b=2; can also be. Again, a=1; b=4; can also be. So this equation is called a complex equation. There are more complicated ones. Actually, both "a" and "b" are variables in this equation. In algebra, multiplication is a "standard" sign. Because if we multiply two numbers, multiplication is done between them, but if we group two numbers, that is, multiply them by a third number, then it is not written. for example: 2(3+6)=2*9=18
Multiplication is usually not used between letters.
From this video I learned the equations of the main section of mathematics.