Use the equation b=u+2 to find the value of b when u=10.

B = u + 2
b and u are known as variables, unknown values used as placeholders.
If the variable u has the value of 10, then you plug the number 10 into the equation in the spot of the placeholder u.
b = u + 2
u = 10
b = 10 + 2
Just add 10 and 2 and you have the value of b!
b = 10 + 2
10 + 2 = 12
b = 12

The value of b is 12.

Hope this helps!