The amortization amount in the first term is #\euro# #40000#

We have to write off #\euro \, 190000-20000=170000#. This is written off over #5# years. We will name the installment #a#. Since the installment decreases by #\euro \, 3000# each time, we must have:
\[a+(a-3000)+(a-6000)+\cdots+(a-12000)=170000\]
On the left hand side of the equation we have the sum of #n=5# terms of an arithmetic sequence with #v=-3000#. Moreover we have #t_1=a# and #t_{5}=a-12000#. According to the sum formula for an arithmetic sequence the left hand side is equal to \[\frac{1}{2} \cdot n \cdot (t_1+t_n)=\frac{1}{2} \cdot 5 \cdot(a+a-12000)=5\cdot a-30000\]
Hence, we have:
\[5\cdot a-30000=170000\]
This is a linear equation with unknown #a#. It can be solved as follows:
\[\begin{array}{rcl}
5\cdot a-30000&=&170000\\
&& \phantom{xxxxx}\color{blue}{\text{the original equation}}\\
5 \cdot a&=&200000\\
&& \phantom{xxxxx}\color{blue}{\text{added } 30000 \text{ to both sides}}\\
a &=& 40000\\
&& \phantom{xxxxx}\color{blue}{\text{both sides divided by }5}\\
\end{array}\]

We conclude that the amortization amount in the first term is #\euro \, 40000#.