1) 5x = 60
x = 60/5=12
7z = 140
z = 140/7=20
2) 23x = 322
x = 322/23=14
47a = 14617
a = 14617/47 = 311
3) 11y + 8y = 1862
19y = 1862
y = 1862/19=98
16x-9x = 840
7x = 840
x = 840/7=120
Учи математику, тут все очень просто!
5/9 * (3.6a - 3 3/5b) - 3.5(4/7a - 0.2b) = 5/9 *3.6a - 5/9 * 3.6b - -3.5*4/7a + 3.5 * 0.2b = 2a - 2b - 2a + 0.7b = -1.3b
7) |-5/12| : |-2.5| = 5/12 * 1/2.5 = 2/12 = 1/6
8) |-6.5| * |2 2/9| = 6.5 * 20/9 = 130/9 = 14 4/9
A5=a1+4d
a15= a1+14*d=a1+4d+10d=a5+10d
d=(a9-a5)/(9-5)=12/4=3
a15=7+10*3=37