Simplify the following: 21− 4.9 ÷ 7 + 3.9 × 0.4 + 0.9

To simplify the expression 21 - 4.9 ÷ 7 + 3.9 × 0.4 + 0.9, we must follow the BODMAS (or PEMDAS) order of operations: Brackets, Orders (powers/roots), Division and Multiplication (left to right), and Addition and Subtraction (left to right).

Step-by-Step Calculation
Division: First, calculate 4.9 ÷ 7.
4.9 ÷ 7 = 0.7

Multiplication: Next, calculate 3.9 × 0.4.
3.9 × 0.4 = 1.56

Substitution: Now, substitute these values back into the original expression:
21 - 0.7 + 1.56 + 0.9

Addition and Subtraction (Left to Right):

21 - 0.7 = 20.3

20.3 + 1.56 = 21.86

21.86 + 0.9 = 22.76