Question 30699
3X+3(X+80)=2940  3 HOURS FOR PLANE 1 AT SPEED X AND 3 HOURS FOR PLANE 2 AT (X+80) EQUALS THE TOTAL DISTANCE APART OF 2940

3X+3X+240=2940 OR 6X=2940-240 OR 6X=2700 OR X=2700/6 OR X=450MPH FOR PLANE 1 & 
450+80 OR 530MPH FOR PLANE 2.