Calculation of Rational Number
To find the result of the expression -1/2 × 3/7 + 3/2 - 3/7 × 1/4, we need to follow the order of operations (PEMDAS - Parentheses, Exponents, Multiplication and Division, Addition and Subtraction).

Step 1: Multiplication of Fractions
-1/2 × 3/7 = (-1 × 3) / (2 × 7) = -3/14
-3/7 × 1/4 = (-3 × 1) / (7 × 4) = -3/28

Step 2: Addition and Subtraction
Now, we substitute the results of the multiplications back into the original expression:
-3/14 + 3/2 - 3/28

Step 3: Finding a Common Denominator
To add or subtract fractions, we need to have a common denominator. In this case, the common denominator is 28. Therefore, we rewrite the fractions with the common denominator:
-3/14 + 42/28 - 3/28

Step 4: Performing Addition and Subtraction
(-3 + 42 - 3) / 28 = 36/28 = 9/7
Therefore, the result of the expression -1/2 × 3/7 + 3/2 - 3/7 × 1/4 is 9/7, which is a rational number.