Substitution: replacing variables with numbers

What is substitution in mathematics?

If n = 4, what is the value of 12 + n?

What does the expression y - 6 represent when y = 10?

How do you express 'a number decreased by 10' in algebraic terms?

What is the algebraic expression for 'twice the sum of 2 and c'?

Calculate 2^2 + 3^2.

What is the value of x if 5 + x = 12?

If a = 3, what is the value of 2a + 4?

What does the term 'variable' mean in mathematics?

What is the result of substituting 5 for x in the expression 3x + 2?