If you work out the fraction of 1600 that 640 you can apply this to the number of 6s, that she based this off of.
640÷1600=0.4
To calculate the number of times she rolled the dice you do 8÷0.4=20.
Therefore she rolled the cube 20 times to get 8 6s.
The answer is D
Because if you replace the variables just by testing them they give the answer as X=-3 and Y=3.
In which replacing:
3(-3)+5(3)=6
and with the other equation we've got:
4(-3)+2(3)=-6
so they comply with the required to be the correct answer, even though you can make a system of equation.
16 would be the only answer the others are there to confuse you
Solution:
1) Switch +10 to -10 and subtract -10 in each side.
Example:
43-10= 33
2) You will be left with
3) Divide
4) Your final answer is -11
So, d = -11