m is an unknown number that is being decreased by 7.
OPTION A IS WRONG BECAUSE MATHEMATICALLY IT IS WRITTEN AS

B IS WRONG BECAUSE IT MEANS

C IS WRONG BECAUSE IT MEANS

BUT D IS THE ANSWER BECAUSE IT MEANS

SINCE m IS TREATED AS AN UNKNOWN NUMBER.
GOODLUCK!!!!
Since both numbers are negative we know that the product will be positive and when something is time 1.5 that is the same as a 50% increase so that is adding half of the original number (4) so the final answer is 6 (4+(half of 4))=6
We have 2x + 4x + 5x = 33 so 11x = 33 and x 3.
The children are 6, 12 and 15
Answer:
a) 
b) 
Step-by-step explanation:
By definition, we have that the change rate of salt in the tank is
, where
is the rate of salt entering and
is the rate of salt going outside.
Then we have,
, and

So we obtain.
, then
, and using the integrating factor
, therefore
, we get
, after integrating both sides
, therefore
, to find
we know that the tank initially contains a salt concentration of 10 g/L, that means the initial conditions
, so 

Finally we can write an expression for the amount of salt in the tank at any time t, it is 
b) The tank will overflow due Rin>Rout, at a rate of
, due we have 500 L to overflow
, so we can evualuate the expression of a)
, is the salt concentration when the tank overflows
Answer:
21 cm²
Step-by-step explanation:
A = (b + B)×h/2
= (5 + 9)×3/2
= 14×3/2
= 7×3
= 21 cm²