I would go with option A for this
There are two ways to find or determine for the value of
c. In the first method, we can use addition and subtraction to isolate the
variable c from the other variables. In the second method, we can use the
transposition of variables to isolate the variable c from the other variables.
So solving for the value of c:
<span>Using 1st method: Addition and Subtraction</span>
We are given:
240 = 6 z + c
Simply subtract 6 z on both sides:
240 – 6 z = 6 z + c – 6 z
Cancelling 6 z – 6 z on the right side:
240 – 6 z = c
or
c = 240 – 6 z
<span>Using the 2nd method: Transposition</span>
240 = 6 z + c
What we are going to do here is to simply transpose the
variable 6 z from the right side to the left side of the equation so that we
are left with c alone on the right side. Always remember that when we
transpose, the symbol becomes opposite. That is:
240 + (- 6 z) = c
240 – 6 z = c
or
<span>c = 240 – 6 z</span>
Identity, <span>For example, x + x = 2x is </span>true for every value<span> of x.</span>
Answer
Find out the what fraction of the sandcastle did they build together .
To prove
Let us assume that the fraction of the sandcastle they build together be x .
As given


Than the equation becomes

L.C .M of (3,7) = 21
solving


Therefore the fraction of the sandcastle did they build together be

Hence proved
Answer for the above question is <u>option C</u>
<u>Step-by-step explanation:</u>
<u>Option C -</u> It's a quadrilateral but not a rhombus . As we know rhombus has congruent sides while its two angle can't be measured 120 degrees but in option C it seems two vertically opposite angles of to be 120 degrees. In rhombus opposite angles are same while adjacent angles are supplementary. All options except C are the rhombus of congruent sides.