The problem is best handled using the method of interpolation which is shown below
$$
\begin{array}{rl}
100^{\circ} C -160.5 \Omega \\
70^{\circ} C - R _{\theta} \\
0^{\circ} C & 60 \Omega \\
\frac{70-0}{100-0} & =\frac{R_{\theta}-60}{160.5-60} \\
\frac{70}{100} & =\frac{R_{\theta}-60}{100.5} \\
R_{\theta} & =\frac{70 \times 100.5}{100}+60 \\
& =130.5 \Omega
\end{array}
$$