His father can drive 25 days without the warning light
Here is a saying 5 and above give it a shove (round up) 4 and below go down low (round down). In your case you would leave it the same, because when rounding you would round to the nearest 10th.
Example:
54 would round down to 50 and 55 would be rounded up to 60.
You can use elimination
7x - 3y = 4
-10x + 3y = 2
Add both equations
-3x = 6, x = -2
Plug in -2 for x in one equation
7(-2) - 3y = 4
-14 - 3y = 4
-3y = 18, y = -6
Solution: x = -2, y = -6
The partial products are: 42 x 28 = (40 + 2) x (20 + 8) = 40 x 20 + 40 x 8 + 2 x 20 + 2 x 8
= 800 + 320 + 40 + 16 Hope this helped.