Hi, Hagrid :) Thanks for posting your question here at Brainly. I hope I could help you with this problem.
The incorrect reason would be letter A: add c/a to both sides.
What he did was transpose the term c/a from the left to the right so that he could separate the terms with variables to the left hand side and the constants in the right hand side.
The number is 4
Step-by-step explanation:
First of all we have to convert the given statement in mathematical form.
Let c be the number then according to given statement

We have to isolate the variable in the equation
Dividing both sides by 2

Adding 3 on both sides

Hence,
The number is 4
Keywords: Linear equation, variables
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Slope-intercept form: y = mx + b
(m is the slope, b is the y-intercept or the y value when x = 0 --> (0, y) or the point where the line crosses through the y-axis)
For lines to be perpendicular, their slopes have to be the negative reciprocal of each other. (Basically flip the sign +/- and the fraction(switch the numerator and the denominator))
For example:
Slope = 2 or 
Perpendicular line's slope =
(flip the sign from + to -, and flip the fraction)
Slope = 
Perpendicular line's slope =
(flip the sign from - to +, and flip the fraction)
y = 1/3x + 4 The slope is 1/3, so the perpendicular line's slope is
or -3.
Now that you know the slope, substitute/plug it into the equation:
y = mx + b
y = -3x + b To find b, plug in the point (1, 2) into the equation, then isolate/get the variable "b" by itself
2= -3(1) + b Add 3 on both sides to get "b" by itself
2 + 3 = -3 + 3 + b
5 = b
y = -3x + 5
Hello!
All the angles inside a triangle is equal to 180
To find x you can do
180 - 50 - 70 = 60
x = 60
To find y you have to find the other missing angle in the other triangle
180 - 50 - 60 = 70
A line is equal to 180°
To find y you do
180 - 60 - 70 = 50
x = 60 and y = 50
Hope this helps!