Sure! Here are the answers to your questions:
a) To express the scientific notation 6.371 x 10^3 in the decimal system of numeration, you can simply move the decimal point three places to the right since the exponent is positive. This will give you 6,371.
b) To convert 6.371 x 10^3 kilometers to meters, you need to remember that 1 kilometer is equal to 1000 meters. Therefore, you can multiply 6.371 by 1000 to convert it to meters. This gives you 6,371 x 1000 = 6,371,000 meters when expressed in decimal notation.
I hope this helps clarify the answers to your questions! Let me know if you need further explanation.