From the two right triangles, you can write the following equations using the Pythagorean theorem. Let's call that shared leg in the middle "y"
y^2 + b^2 = a^2
y^2 + c^2 = x^2
y^2 + b^2 = a^2
re-write this to get "y" alone for substitution.
y^2 = a^2 - b^2
substitute (a^2 - b^2) for y^2 in the other equation. y^2 + c^2 = x^2
a^2 - b^2 + c^2 = x^2
Now put in the values given for a,b,c to solve for x
(7.1)^2 - (5.6)^2 + (5.7)^2 = x^2
51.54 = x^2
square root
7.2 = x
Among many other formulas, the area of a triangle is

where B is the angle between sides a and c.

Answer: 92.05 sq cm, first choice
Bonus. Here's a formula for the area S of a triangle your teacher doesn't know:

Answer:
(x,y) + (x-4, y)
Step-by-step explanation:
horizontally means it would be on the x axis traveling to the left would be your subtracting there fore the only answer which comes with a x-4 is (x,y) + (x-4, y)
Answer:

Step-by-step explanation:
The question is to find the equation of the line going through the points (3,-1) and has a slope of -1.
First, the equation of a line is given as:
Equation = y = mx + b
Where
m is the slope
b is the y-intercept (y-axis cutting point)
We know the slope, so the equation becomes:
y = mx + b
y = -1x + b
y = -x + b
Now the point given is in the form (x,y), so
x = 3
y = -1
We substitute and find b:
y = -x + b
-1 = -3 + b
-1 + 3 = b
b = 2
Final Equation:
y = -x + 2