Aset of equations is given below:
equation e: c = 2d + 1
equation f: c = 3d + 7
which statement describes a step that can be used to find the solution to the set of equations?
equation f can be written as c = 3(c − 1) + 7.
equation f can be written as c = 2(c − 7) + 1.
equation f can be written as d + 1 = 3d + 7.
equation f can be written as 2d + 1 = 3d + 7.

The correct answer is 'Equation F can be written as 2d + 1 = 3d + 7'. In order to find the answer to a system of equations, the two equations must be set equal to each other. For instance, if we had the equations x = y + 1 and x = 3y - 1, we would set the two equations equal to one another to find the answer.

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

x = y + 1
x = 1 + 1
x = 2

We can use this to solve the set of equations above.

2d + 1 = 3d + 7
1 = d + 7
-6 = d

c = 2d + 1
c = 2(-6) + 1
c = -12 + 1
c = -11

Hope this helps!

C. i believe it is (5×(-20))+(100×(0.7))

Element 17 is chlorine it is a group 7 element(halogen) and belongs to period 3 of the periodic table