For the first one, the answer is -1 1/5
for the second one, the answer is 2.75
for the third one and fourth one,
To divide fractions take the reciprocal (invert the fraction) of the divisor and multiply the dividend. This is the quickest technique for dividing fractions. The top and bottom are being multiplied by the same number and, since that number is the reciprocal of the bottom part, the bottom becomes one
You cannot have infinite solutions.
Answer: Use a compass to measure the length of AB. Draw an arc from point B (or point A) with that distance. Extend line AB through that arc and label the intersection as point C. AC is twice the length of AB.