Tommy had 40 oranges to give to 3 groups of children. - The first group ate 30% of the total oranges.
- The second group ate 7 of the total oranges.
- The third group ate 1/8 of the total oranges.
How many oranges were left?

16

Step-by-step explanation:

1st group = 30% or .3 as a decimal

.3 * 40 = 12

2nd group = ate 7

Third group = 1/8 or .125 as a decimal

.125 * 20 = 5

12 + 7 + 5 = 24

40 -24 = 16

853.3

step-by-step explanation:

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.