First, we need to determine the marked-up price of the snowboard. The original cost of the snowboard is $120, and it was marked up by 25%.
To calculate the markup, we find 25% of $120:
\[ \text{Markup} = 0.25 \times 120 = 30 \]
Now, we add the markup to the original cost to find the marked-up price:
\[ \text{Marked-Up Price} = \text{Original Cost} + \text{Markup} = 120 + 30 = 150 \]
Next, we need to calculate the price after applying the 70% discount on the marked-up price of $150.
To find the amount of the discount, we calculate 70% of $150:
\[ \text{Discount} = 0.70 \times 150 = 105 \]
Now, we subtract the discount from the marked-up price to find the final sale price:
\[ \text{Final Price} = \text{Marked-Up Price} - \text{Discount} = 150 - 105 = 45 \]
Thus, the price of the snowboard after the discount is \(\boxed{45}\).