p +d = 74 coins
rewrite as p =74-d
0.01p + 0.10d = 4.61
0.01(74-d) +0.10d = 4.61
0.74 - 0.01d +0.10d =4.61
0.74 +0.09d =4.61
0.09d = 3.87
d = 3.87/.09 = 43
p = 74-43 = 31
43 dimes and 31 pennies
use the quadratic formula, we must.
-13 +/- √(169 +48) / 2
-13 +/- √217 / 2
-13 +/- 14.73 / 2
(-13 + 14.73) / 2 = 0.865
(-13 - 14.73) / 2 = -13.865
the solutions, we have found.
helped, i hope i have.
1.5x + 0.2y = 2.68....multiply by 0.3
1.6x + 0.3y = 2.98...multiply by - 0.2
------------------------
0.45x + 0.06y = 0.804 (result of multiplying by 0.3)
- 0.32x - 0.06y = - 0.596 (result of multiplying by - 0.2)
----------------------add
0.13x = 0.208
x = 0.208/0.13
x = 1.6
1.5x + 0.2y = 2.68
1.5(1.6) + 0.2y = 2.68
2.4 + 0.2y = 2.68
0.2y = 2.68 - 2.4
0.2y = 0.28
y = 0.28/0.2
y = 1.4
solution (they intersect at) (1.6,1.4)
Take the square root of both sides to solve and you get a= 0.4,-0.4
