If (a) is (0.9) unit to the left of (1.6) on the number line, what is (a)?

Correct answer: (0.7)

The direct answer is option C,
\(0.7\). On a number line, moving left means moving to a smaller number, so subtract the distance from the starting number:
\(a=1.6-0.9=0.7\). We can check it because the distance from
\(0.7\) to
\(1.6\) is
\(1.6-0.7=0.9\), and
\(0.7\) is indeed on the left. Option A,
\(2.5\), is obtained by adding and lies to the right, so it is wrong. Option B,
\(0.9\), is the distance moved, not the final coordinate. Option C is correct because it is the starting value minus the leftward distance. Option D,
\(-0.7\), subtracts too much and is not 0.9 units left of 1.6; its distance is
\(2.3\). Exam cue: right means add, left means subtract.