Step-by-step explanation:

The rate of the motorboat on still water is 1375

The current rate of the motorboat is 2025
Answer: 1668.2
Multiply 1668.2×45 and get 75,069
Are you sure you want ONLY the coefficient of b? If you expand this, you will have b in 3 of 4 terms.
According to Pascal's Triangle, the coefficients of (a+b)^4 are as follows:
1
1 2 1
1 3 3 1
1 4 6 4 1
So (a+b)^4 would be 1a^4 + 4a^3b + 6a^2b^2 + 4ab^3 + b^4
Here, you want (3 + b)^4. Here's what that looks like:
3^4 + 4[3^3*b] + 6[3^2*b^2] + 4[3*b^3] + 1[b^4]
Which coeff did you want?
Oof this one is hard I think it’s 20 mm but I’m not sure
This is an excellent practice for the solution of quadratic equations.
1*36=36 => (1,36)
2*18=36 => (2,18)
3*12=36 => (3,12)
4*9=36 => (4,9)
6*6=36 => (6,6)
9*4=36 => (9,4)
12*3=36 => (12,3)
18*2=36 => (18,2)
36*1=36 => (36,1)
We can see that the sum decreases until the two factors are close (or equal) and then increases again.
The pair of integers with a sum of 20 is therefore (2,18) or (18,2).