\begin{aligned} 7.5+k& =10 7.5+k-7.5& =10-7.5& \green{\text{step } 1} k& =2.5& \blue{\text{step } 2} \end{aligned}
7.5+k
7.5+k−7.5
k


=10
=10−7.5
=2.5


step 1
step 2


find annie's mistake.
choose 1
choose 1

(choice a)
a
\green{\text{step }1}step 1start color #28ae7b, start text, s, t, e, p, space, end text, 1, end color #28ae7b

(choice b)
b
\blue{\text{step }2}step 2start color #6495ed, start text, s, t, e, p, space, end text, 2, end color #6495ed

(choice c)
c
annie did not make a mistake.