An equation is a math sentence that says that 2 things are equal. An equation always has an equal (=) sign. The thing or things that are on the left side of the equal sign are equal to the things on the right side of the equal sign. Here are a few equations:
X = Y + 5
A = B - 4
Z = 3 A
C = 
D (circumference of a circle)
A = W H (area of a rectangle with width W and height H)
E = M C2 (Einstein's famous equation)
In the first equation, if Y is 2, then X must be 2 + 5 or 7 to make the equation true.
In the second equation, if B is 10, then A must be 6 to make the equation true.
In the third equation, the number next to the letter means multiply the value of the
variable represented by "A" by 3. So if A is 4, then Z must be 12 to make the third
equation true. Now here's a problem for you:
In the first equation, if Y were 10, what would X be?