Rounded to the tenths place is 8015.8
6x15= 90
9x20= 180
180+90= 270
270 - 25 = 245 dane has 245 stamps left
Serious high school. This is one of the few differential equations I can solve.
The usual particular solution is 
because 
is its own derivative.
An independent solution is 
which has a negative sign in the first derivative which turns back to positive in the second.
The arbitrary linear combination spans the solution space:
But we only are asked for the basis.
Answer:
Let number of yellow marbles = x
Let number of red marbles = y
Let number of blue marbles = z
Given that Finley has 152 yellow, red, and blue marbles in a bag.
So we get equation:
x+y+z=152...(i)
"He has seven more red marbles than yellow marbles" means:
y=x+7...(ii)
"three times as many blue marbles as yellow marbles." means:
z=3x...(iii)
Now we just need to solve those equations to find the answer.
Plug (ii) and (iii) into (i)
x+(x+7)+(3x)=152
x+x+7+3x=152
Which looks similar to choice (B)
5x+7=152
5x=145
x=29
Hence final answer is choice B.
Required equation is
x+x+7+3x=152
Number of yellow marbles = 29
