How far was Russia responsible for the failure of the Schlieffen Plan?

Explanation:

The Schlieffen Plan's strategy required that France be defeated swiftly – but this didn't happen. That failure led to sustained trench warfare on the Western Front. In those grim battles of attrition, such as the Battle of the Somme and the Battle of Verdun, Allied forces ultimately outnumbered the Germans.

for this case we have the following equation:

we apply distributive property to the terms within parentheses.

subtracting 2 on both sides of the equation:

straight down to hell mate