Answer:
300 SUVs were sold.
210 Passenger cars were sold.
Explanation:
Let S denote the amount of SUVs sold and let P denote the amount of passenger cars sold.
The total amount of vehicles sold was 510, so:

90 more SUVs were sold than passenger cars. In other words:

We know have a system of equations. We can solve it buy substituting the second equation into the first. Thus:

Combine like terms:

Subtract 90 from both sides:

Divide both sides by 2:

So, the 210 passenger cars were sold.
This means that 210+90=300 SUVs were sold.
And we're done!