Answer:
300 SUVs were sold. 
210 Passenger cars were sold. 
Step-by-step 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!