Answer:
15.
16. 10 ml of 20% saline and 40 ml of 10% saline
Step-by-step explanation:
A chemist takes x ml of 20% saline and y ml of 10% saline. In total, he takes
x + y ml that is 50 ml, so
There are 
ml of salt in x ml of 20% saline and 
ml of salt in 10% saline. There are 
ml of salt in 50 ml of 12% saline. Thus,
15. We get the system of two equations:
16. Solve this system. From the first equation:
Substitute it into the second equation:
If a single board measures 1/12 of a meter then it would take 12 boards to make a meter. Since, the stack is 2 meters high. You would multiply 12 and 2 to get 24. There is 24 boards in the stack.
Answer:
58
Step-by-step explanation:
follow the pattern. The pattern is to take away 10, for each subsequent number.
Answer: x= -6; y= -1
Step-by-step explanation:
-4x + y = 23
4x - 9y = - 15
-4x + y = 23
y = 23 + 4x [Add 4x to both side]
4x - 9(23 + 4x) = - 15
4x - 207 - 36x = - 15
-32x - 207 = -15
-32x = 192 [Add 207 to both side]
x = -6 [Divide -32 from both side]
-4x + y = 23
-4(-6) + y = 23 [Plug in -6 for x]
24 + y = 23 [Subtract 24 from both side]
y = -1
