Question

vertical/adjacent/complementary angles (algebraic)
score: 1/5 penalty: 0.25 off
question
solve for the value of r.
answer attempt 1 out of 2
r =

Explanation:

Step1: Identify angle relationship

The two angles are complementary, so $(5r + 7)+(7r - 1)=90$.

Step2: Simplify the left - hand side

$5r+7 + 7r-1=12r + 6$. So, $12r+6 = 90$.

Step3: Isolate the variable term

Subtract 6 from both sides: $12r=90 - 6=84$.

Step4: Solve for $r$

Divide both sides by 12: $r=\frac{84}{12}=7$.

Answer:

$r = 7$