In mathematics when we use the numbers and letters to show the relationship between two quantities, the expression is called algebraic expression.
The sum of the M and 7.1 is M+7.1
We don’t know the value of M so we don’t know the exact value for sum of M and 7.1
When we writ this in algebraic expression,
let S is the sum of M and 7.1
then the equation will be:
M + 7.1 = N