A variable is a letter that represents an unspecified number. Substitute a number for each variable and perform the arithmetic operations in order to evaluate the expression. For instance, to evaluate the expression x^{2} + 2x - 3y for x = 1 and y = 2, calculate the expression by substituting the given x and y: x^{2} + 2x - 3y = 1^{2} + 2×1 - 3×2 = 1 + 2 - 6 = -3. Evaluate each expression below if a = 4, b = 2 and c =-1: Question 1: 4 6 9 Question 2: 16 21 24 29 Question 3: 8 -10 -2 -6 Question 4: 0.5 2 0.4 3.5 Question 5: 385 401 423 459 Question 6: 88 94 98 102 Question 7: 0.675 0.75 0.875 0.925 Question 8: 0.5 0.6 0.7 0.8 Question 9: -3.2 -3.6 -3.9 -4.3 Press the Submit button to see the results.