$\{\begin{array}{l}y=3x\\ y+x+26=90\end{array}$

$\{\begin{array}{l}y=3x\\ y+x=90-26\end{array}$

$\{\begin{array}{l}y=3x\\ 3x+x=64\end{array}$

$\{\begin{array}{l}y=3x\\ 4x=64\end{array}$

$\{\begin{array}{l}y=3\cdot 16\\ x=16\end{array}$

$\{\begin{array}{l}y=48\\ x=16\end{array}$

Wiek ojca obecnie: $y+3=48+3=51$
Odp.: Ojciec ma obecnie $51$ lat.