Step 1: Rewrite the 2 lines in proper form

Rewrite the 2 lines as:

y = -2 + (-3/4) * x
x = -7/4 + (-3/4) * y

so b1 = -3/4 and b2 = -3/4

Step 2: Apply Pearson's Coefficient formula

Let p = pearson coefficient
Let x_std = standard deviation of x
Let y_std = standard deviation of y

From this tutorial we have:

p = b1 (x_std / y_std)
p = b2 (y_std / x_std)

Multiplying these 2 equations together we get
p^2 = b1 * b2
p^2 = (-3/4) * (-3/4)
p^2 = 9/16
p = 3/4 or -3/4 (depending on correlation of x and y)

Step 3: Find out if p is postive or negative

Notice that both of the original line equations have negative slopes, so x and y are negatively correlated by definition. So, p = -3/4

From my HackerRank solutions.