1)-4,81*(-2,3)-(-2,3)*5,19= ( -3/8+2 1/16)*16= -3/8 *(-6,81)+(3,19)*(-3/8)= (-5/12+3/7)*8,4= 2)(x+4)*(x-3)=0 (3/8y-9/16)*(y-0,8)=0

а)
1. - 4,81 * (- 2,3) + 2,3 * 5,19 = 11,063 + 11,937 = 23.
2. (- 3/8 + 2 1/16) * 16 = 13.
    2 1/16 = (2 * 16 + 1)/16 = 19/16.
 1: - 3/8 + 19/16 = - 6/16 + 19/16 = 13/16.
 2: 13/16 * 16 = 208/16 = 13.
3. - 3/8 * (- 6,81) + (3,19) * (- 3/8) = - 3/8 * (3,19 - 6,81) = - 3/8 * (- 3,62) = 1,3575.
4. (- 5/12 + 3/7) * 8,4 = 1/10.
    8,4 = 8 4/10 = 84/10
 1: - 5/12 + 3/7 = - 35/84 + 36/84 = 1/84.
 2: 1/84 * 84/10 = 84/840 на 84 = 1/10.
б)
1. (x + 4) * (x - 3) = 0
    х + 4 = 0, х = - 4; х - 3 = 0, х = 3.
2. (3/8y - 9/16) * (y - 0,8) = 0
 1: 3/8y - 9/16 = 0, 3/8y = 9/16, y = 9/16 / 3/8 = (9 * 8)/(16 * 3) = 72/48 на 24 = 3/2 = 1 1/2.
 2: y - 0,8 = 0, у = 0,8.