please check my answers

Question

Suppose that the temperature outside is dropping at a constant rate. At noon, the temperature is 70 F and it drops to 58 F at 5 p.m. How much did the temperature change each hour?
12/5=2.4 degrees per hour.

Evaluate the expression if a=-2, b=5,c=-4, and d=6:4b+5d-c/a


4b+5d-c/a =

4(5)+5(6)-(-4)/(-2)
4x5=20
5x6=30
-4/-2=2
answer= 20+30+2=52

Evaluate the expression if a=-2, b=5,c=-4, and d=6: 6^2-2bc+c^2

---> 5² - 2(5)(-4) + (-4)²
= 25 + 40 + 16
= 81

The simple interest I on a principle of P dollars at interest rate r for time t, in years, is given by I=Prt. Find the simple interest on a principle of $6000 at 3% for 2 years. (Hint: 3%=0.03)
Interest = 6000*.03*2

Simplify using the distributive property:7(4w-3)-25=
-21+25w+28w=
-21+3w
A triangle has sides 3x+7, 4x-9, and 5x+6. Find the expression that represents the perimeter.

=3x + 7+ 4x - 9+5x +6
=3x+4x+5x +7-9+6
=12x-3


Simplify, if possible: 6x^2y^3+9x^2y^3/3x^2y^2

Answer 1

The temperature one is correct. You may want to include a negative sign to indicate that the temperature is dropping.

You made a sign mistake on the first evaluation. (You dropped one of your negative signs.)

On the second evaluation, you changed "6^2" to "5^2" in your work.

For the simple interest, you should multiply what you have to get a numerical answer in dollars.

Your distributive property problem is quite wrong. The distributive property states for an expression a(b+c), the answer will be ab + ac. Try to apply that to your problem.

On the perimeter, check 7-9+6. It's not -3.

Answer 2

-x+2y=3
3x+2y=-1