Ants versus humans
the average mass of an adult human is about 65 kilograms while the
average mass of an ant is approximately 4 x 10-3 grams. the total
human population in the world is approximately 6.84 billion, and it is
estimated there are currently about 10,000 trillion ants alive. 1
my question: based on these values, how does the total the total mass of all living
ants compare to the total mass of all living humans?

31/6= 19/6 19/6 *1/7=19/42

Ok here we go ..there are plenty of ways to solve such math problems but we will go for the smartest and easiest ..5x+2y=7  -2x+6y=9we rearrange them into the following ..by multiplying the 1st equation by 2 it becomes 10x + 4y = 14we rearrange it and so it becomes 10x = 14 - 4yas for the second equation we multiply it by 5 and rearrange it so it becomes as to the following ..-10x + 30y = 45rearranging so 10x = 30y -45now 10x equals both 14 - 4y and 30y -45so   14 - 4y = 30y -4531 = 26yy= 31/26 = 1.19 or around 1.2so by now we can calculate x easily as  -2x+6y=9so 2x = 6y -9 = 6 * 31/26 - 9 = -1.84  then x = - 0.92 or around -0.9best luck!