How do you get to that answer? 1/4 - 1/14 = 5/28 yellow. what am I doing wrong? regards!

It's basic arithmetic. The key point is that the fraction remains equal when its top (numerator) and bottom (denominator) are multiplied by the same number.

To add or subtract different fractions, you must make their denominators the same. This can be done either by multiplying the top and bottom of one fraction with the same multiplier in such a way that the denominator of two fractions can be made equal. We would need a least common multiple of both denominators (here 4 and 14) so that we can make these equal and solve them conveniently. The least common multiple of 14 and 4 is 28. This means we can make both denominators equal to 28 and perform our operation of subtraction here. Following this, let's review the procedure now:

1/4 - 1/14

Multiply 1/4 fraction top and bottom with 7 to get the denominator equal to 28 in this fraction. Multiply top and bottom with 2 in (1/14) fraction to make its denominator equal to 28. This will make the above operation equal to:

7/28 - 2/28 = 5/28