7^-2х=21+3^-1 плисс помогите

1) 6/11 * 3/22 = 12/17 : х; 6/11*х = 3/22 * 12/17; х = 3/22 * 12/17 * 11/6; х = 3/17.2) 21/х + 3 = 7/4; 7(х + 3) = 21 * 4; х + 3 = 21 * 4 : 7; х + 3 = 12; х = 12 - 3; х = 9.3) 12/13 = (7,4 - х)/2,6; 7,4 - х = 12 * 2,6 : 13; 7,4 - х = 2,4; х = 5.4) 48 : 35 = 1/14х : 1/16; 1/*4х * 35 = 48 * 1/16 ; 5/2*х = 3; х = 3 : 5/2; х=12