Question 18576
Ok, let x = the total number of marbles in the jar. You can write an equation for the total number, x, like this:

{{{x = (1/3)x + (1/4)x + 10}}} Now all you need to do is solve for x. Add: {{{(1/3)x + (1/4)x = (4/12)x + (3/12)x)}}} = {{{(7/12)x}}}
{{{x = (7/12)x + 10}}} Subtract {{{(7/12)x}}} from both sides.
{{{x - (7/12)x = 10}}}
{{{(5/12)x = 10}}} Finally, multiply both sides by the multiplicative inverse of {{{5/12 = 12/5}}}
{{{x = 10(12/5)}}}
{{{x = 24}}}

There are 24 marbles in the jar.

Check:

{{{(1/3)(24) + (1/4)(24) + 10 = 8 + 6 + 10 }}} = 24 The total number of marbles in the jar.