A vitamin's expiration date has passed. The label states each tablet contains calcium 450 mg, but 125 mg of calcium deteriorates after the expiration date. What is the current total amount of calcium left per tablet?

 

Looking at the four given decimals, we can arrange them from the smallest to the largest as

\(0.0788<0.76<0.767<0.79\)

Thus, 0.79 is the largest decimal.

Compare the four fractions, find the least common divisor for denominators 5, 6, 7 and 8 which is 840.

Now multiply each fraction with 840 as:

3/5 * 840=504

3/6 *840=420

3/7 * 840=360

3/8 * 840=315

From the above calculations, 504 is the greatest, which follows that 3/5 is the largest fraction.

\(\frac{0.9}{0.15}=6\)

A ratio of the form a:b=c:d is converted to a proportion as

\(\frac{a}{b}=\frac{c}{d} \)

where b and d are not equal to zero. Now applying the same concept to 7:10=21:X yields,

\(\frac{7}{10}=\frac{21}{X}\)

Find the value of X by cross-product

\(7X=21\ast10\)

Divide both sides by 7

\(\frac{7X}{7}=\frac{210}{7} X=30 \\Thus,\ the value\ of \ X is \ 30. \)