The amortization amount in the first term is #\euro# #30500#

We have to write off #\euro \, 260000-30000=230000#. This is written off over #20# years. We will name the installment #a#. Since the installment decreases by #\euro \, 2000# each time, we must have:
\[a+(a-2000)+(a-4000)+\cdots+(a-38000)=230000\]
On the left hand side of the equation we have the sum of #n=20# terms of an arithmetic sequence with #v=-2000#. Moreover we have #t_1=a# and #t_{20}=a-38000#. According to the sum formula for an arithmetic sequence the left hand side is equal to \[\frac{1}{2} \cdot n \cdot (t_1+t_n)=\frac{1}{2} \cdot 20 \cdot(a+a-38000)=20\cdot a-380000\]
Hence, we have:
\[20\cdot a-380000=230000\]
This is a linear equation with unknown #a#. It can be solved as follows:
\[\begin{array}{rcl}
20\cdot a-380000&=&230000\\
&& \phantom{xxxxx}\color{blue}{\text{the original equation}}\\
20 \cdot a&=&610000\\
&& \phantom{xxxxx}\color{blue}{\text{added } 380000 \text{ to both sides}}\\
a &=& 30500\\
&& \phantom{xxxxx}\color{blue}{\text{both sides divided by }20}\\
\end{array}\]

We conclude that the amortization amount in the first term is #\euro \, 30500#.